It's over a year now since I first discovered that I'd been the victim of a plagiarist. The culprit called herself Joanne Clancy, although I didn't know at the time if that was her real name.

All I knew is that she'd taken a series of Dublin-based crime novels, which I had co-written over a decade earlier under the pen name Ingrid Black, and was publishing them on the online bookseller Amazon almost exactly word for word, changing only the names of the characters and locations of the stories. She'd made thousands of euro before being rumbled by an eagle-eyed reader who'd contacted me on Twitter.

Eventually, I managed to have the books removed from sale, along with a score of other titles by the same fake author, some of which I strongly suspected had also been plagiarised from other writers' books.

Who was she? Why did she do it? I'd resigned myself to never finding out. Once exposed, Joanne Clancy vanished as suddenly as she'd appeared. I wrote about my experience with this mysterious book thief in Life magazine last year and thought that was the end of it.

It turned out that I was wrong.

Exactly a week after the original article was published, I was approached via social media by a reader who wished to remain anonymous. She wanted to draw my attention to a woman who'd appeared recently on Facebook.

Uncanny resemblance

This newcomer's name was 'Kate Acton' and she'd popped up the day before the previous Christmas Eve and was now busy befriending members of a group known as 'The Book Club on Facebook'. 'Kate', who claimed to live in Galway, was an aspiring author, she said, and was in the process of writing her first novel, a thriller called Whyte Lies, due to be self-published in April 2016.

'Kate' was very approachable and friendly. She even had her own website. The problem was that she'd also posted some pictures of herself, and those pictures, this reader thought, bore an uncanny resemblance to those that had previously been used by Joanne Clancy. She sent them to me so that I could check them out for myself.

Sure enough, the similarity was striking. I couldn't understand why, if this was indeed Joanne Clancy, she'd done something so stupid. But what was even more suspicious was that 'Kate' took an abrupt break from Facebook on Easter Sunday, the same day that my article about Joanne Clancy appeared in Life.

She'd cooked lamb shanks, she explained, and next thing, she was in hospital with food poisoning.

"I've been that sick, I haven't read a word since Sunday," she said on Facebook, by way of explaining her absence, after months of regular updates and interactions.

Of course, it also helped explain why she wasn't around to participate in some of the heated discussions about plagiarism within the Facebook book club that my article had provoked. The reader who contacted me thought it all a bit odd. Everyone had something to say about the matter, except for the newcomer 'Kate'.

Still, it didn't mean that 'Kate Acton' definitely was Joanne Clancy. I told the reader that I'd keep my eye on the situation and see how things developed. What I didn't tell her was that from the moment I saw those pictures of 'Kate' and checked out her website, I was as certain as I could be that I was, once again, dealing with Clancy.

For a start, her website was almost a carbon copy of Joanne Clancy's. It followed the exact same template.

Both women were avowed Francophiles. Both had the same habit of posting saccharine self-help quotes, stories and blogs. Their girlishly enthusiastic style of writing was interchangeable. Even their descriptions of themselves seemed similar. Joanne Clancy had described herself as "an avid reader, a self-confessed Kindle addict and a tea fiend". 'Kate Acton' said: "I'm a serial-killer thriller addict, avid reader, and aspiring author".

It was certainly not enough to declare them one and the same person, but there were more than enough clues there to pique my interest and keep me digging.

I was even intrigued by the name under which the book was to be published: 'KC Acton'. A new KC to follow the old JC (Joanne Clancy)? The name was even an anagram for "K-con act" and "Take on act" (What can I say? I like crosswords and word games. Details fascinate me).

I invented a new identity, signed up to Facebook and became a member of the same book club. Shortly after that, I befriended 'Kate Acton' so that I could see her posts. I also took screenshots of the five pictures that she'd posted in case she later deleted them.

Three were of herself, one was with her mother and sister, and the last one was of her cat. I also took a note of the other pictures she'd posted. These included one of her fireplace - a very distinctive one, built from red brick, running the full width of the chimney breast before tapering off towards the ceiling. At its foot, there was a very attractive wood-burning stove.

Little did 'Kate Acton' know that these two images would allow me to jigsaw together some vital clues that would tie her to Joanne Clancy.

Not quite right

'Kate Acton' was careful on Facebook. She didn't post a lot after Easter Sunday, nor did she reveal very much personal stuff. Most of her 'friends' were members of the book club and most of her interactions were book related. In the months that followed, it was this unusually narrow list of friends that made some other readers wary enough to approach me and confess their concerns about 'Kate'.

There was, they said, something not right about her. She professed to be a novice in the publishing game, but at the same time seemed to know a lot about publicising her forthcoming novel. She had an active Twitter account, also set up the previous December. Her second novel was scheduled for release only a few months later, hot on the heels of the first, and this concerned some people too.

How was this first-time author able to produce her second book so quickly? These people were suspicious that 'Kate' was not quite the woman she claimed to be.

All of them had read my original article in LIFE magazine, and were now extra vigilant about what they saw as overly prolific writers. Plagiarism seemed more rife among self-published authors than they'd suspected.

After my encounter with Joanne Clancy, I'd wondered if stealing my books was out of character - she insisted in the only email I received from her that she'd never done it before and that she was thoroughly ashamed of her actions - or was she a professional con artist who'd discovered an easy way to make money?

Whyte Lies would answer those questions.

For some reason, though, the publication of 'Kate Acton''s book was put back to July, which meant I had almost three months to fill between being alerted to her existence and getting my hands on her debut. In the meantime, I became quietly obsessed with finding out as much as I could about her.

Hunches are all very well, but they're not proof. I got into the habit of looking through Joanne Clancy's old website. I'm not sure what I was hoping to find, especially since it was no longer updated, but I kept looking anyway.

One night, having woken up about 3am and finding myself unable to go back to sleep, I came across a photograph she had posted of her Christmas tree.

It wasn't the Christmas tree that grabbed my attention, though, because lying on a mat in front of the fire was a cat. It looked awfully familiar.

Quickly, I logged on to Facebook and my suspicion was confirmed. The cat in 'Kate Acton''s photograph was identical to the one on Joanne Clancy's website.

I went back and forth between both images multiple times, checking markings and any other similarities to make sure that they were the same animal.

And it was while doing this that something else in the picture began to look familiar. The more I examined the image of the cat in front of the fire, the more I started looking at the fireplace itself. I'd seen that wood-burning stove before. I'd seen the brick fireplace before, too. Could it be the same one that had appeared in 'Kate Acton''s photograph? It could, and it was.

This still wasn't proof that these two people were one and the same, but it was strong circumstantial evidence tying them together. It gave me something to work with.

It wasn't the only time that fireplace would make an appearance, either. When 'Kate Acton' appeared on Facebook, she had a story to tell about her life, and she went into even greater detail about it on her website.

"This time last year, I was stuck in a dead-end job and a dead-end relationship with the self-declared love of my life. It all came to a head one day when I'd finally had enough. I was sitting at the train station, on my way home, when I decided I didn't want the life I had any more. I was sick of the abuse, the mood swings, and the bickering. For too long I'd been afraid to leave, afraid to strike out on my own, afraid to be alone, afraid of change." Finally, she said, she'd found the courage to dump her boyfriend and embrace the life of a singleton.

'Kate Acton' had milked this touching story dry to explain her shiny new self to her online friends. I wondered if this was true, knowing how fond she was of inventing stories about herself, as well as stealing books.

After my first article was published in Life, though, some people came forward and divulged details about Joanne Clancy's personal life. I found out, for instance, that Joanne Clancy did appear to be her real name, which made what she'd done particularly reckless. I was given locations where she might be found by people who said they knew her. I was given an address, which I was informed was her mother's house. I was also told about the man with whom she was apparently living.

His online presence furnished further clues as to their location. Some of his own photographs also showed that by-now-familiar fireplace.

They must have been together for quite a number of years, because he talked about having lived in a camper van for a while, as Joanne Clancy had. Someone, who knew the couple personally, also came forward to tell me a bit about Joanne. She was a quiet woman, he said, with a quick wit, but who kept herself very much to herself.

She was neat, polite and friendly. "On meeting her, she feels like a really nice, hard-working person," he told me. She didn't mix much with the locals in the small place where she and her boyfriend lived, and instead "locked herself away almost 100pc in writing".

She went as far as to claim that writing had saved her from working in a factory.

Once again I found myself wondering if the story 'Kate Acton' had told about her newly single status was actually true. It certainly seemed that Clancy and her boyfriend were still living in the same house. She'd posted pictures of the fireplace since becoming 'Kate Acton', but 'Kate Acton' was supposedly single.

He'd also posted pictures of the fireplace since 'Kate Acton' had emerged. Cross-referencing pictures of the interior of their house with pictures of houses for sale in the local area - hurray for property websites - narrowed the search down further.

Thinly disguised

Each time I uncovered a new piece of information about 'Acton'/Clancy it emboldened me to try and find out more. It was back to Joanne Clancy's old website to see if I'd overlooked anything else. As you'd expect, this featured a number of extracts from her old books.

I'd read some of them before, but had been unable to work out whether she'd plagiarised anybody else's work. Certainly, nothing jumped out at me. I'm an avid reader, as she would say, but no one can read every book.

One night I came across an extract I'd never noticed before. It was from Watched, a book published by Joanne Clancy a couple of years ago. I started reading and immediately recognised it as a thinly disguised retelling of the murder of Sophie Toscan Du Plantier, the French woman brutally killed while spending a few days over Christmas at her holiday home in west Cork in 1996.

No one has ever been convicted of the crime, but the similarities would have been instantly recognisable to any Irish reader; and, of course, there is nothing wrong with an author using a real case as the basis for a work of fiction. Crime writers do it all the time. Something told me, however, that Clancy had done more than simply use real-life details while carving out her own story. There were descriptive passages, for instance, that I simply didn't believe Clancy to be capable of writing on her own. Somebody who could write that well would have no need to steal somebody else's work. I did a quick search on the internet for non-fiction books that had been written about the case, and the first one that came back was Death In December by Michael Sheridan, a one-time Sunday Independent journalist and now a theatre director.

After buying a copy, It didn't take me long to realise that Clancy had indeed stolen Sheridan's work, too. Entire passages had been lifted from his book, originally published by the O'Brien Press, with only minor changes.

I thought back to the only email I'd ever got from her, dated November 5, 2015, in which she told me three things. The first was that she only earned a few hundred euro from the Ingrid Black novel she'd plagiarised. I subsequently found out from Amazon that she'd actually been paid nearly $2,000, so I knew that was a lie.

The second thing was that her sister had recently been diagnosed with cancer. I'd been contacted privately by another person to say that this was not true. Clancy's sister was, thankfully, healthy and working in a restaurant. The last thing Clancy said was that she'd never plagiarised anybody else's work before. I now had proof that this was also a lie. I started to feel 'had' all over again.

I'd always suspected that her email was manipulative, a thinly disguised attempt to make me feel sorry for her and not pursue legal action. It had worked. I'd almost felt sympathy for the woman. Now realising that everything she'd told me was, in all likelihood, fiction, I started to get angry all over again. Clearly, her entire 'writing' career had been built on stealing other people's books, not only mine.

A few days later, 'Kate Acton' published the blurb of her new book, Whyte Lies. The story concerned the investigation by Detective Chief Inspector Faith Whyte into the shooting dead of a family in their car in woods in a remote part of Killarney National Park in Co Kerry. The only survivors are two young girls, one bludgeoned unconscious and left outside the car, the other found alive, cowering under the skirt of her dead mother inside.

I recognised these details as that of the British-Iraqi family who'd been gunned down in similar circumstances on a quiet mountain track near Lake Annecy in France while on holiday. The case remains unsolved.

Again, there's nothing wrong with taking fictional inspiration from a real-life event, even if most authors would normally take more care to fashion it into something new, rather than lifting the entire episode, detail by detail, from news reports. But if 'Acton' had constructed this story in the same way that Clancy had done with the Sophie Toscan du Plantier book, then I knew she'd have needed a non-fiction book to help her.

A quick search on the internet for books about the Annecy murders revealed there were not many, but the most prominent was The Perfect Crime by Tom Parry, a special correspondent with the Daily Mirror in London and a past winner of the 'Feature Writer of the Year' title at the UK Press Awards. I ordered a copy to read in advance of the publication of 'Acton''s book, suspecting this would be her main source. Frustratingly, I still had a month to wait before comparing both texts.

Whyte Lies finally came out at the beginning of July, and any trace of doubt vanished. Not only had 'Acton' plagiarised large parts of Tom Parry's book, as I'd expected, she'd even included huge undigested chunks of Watched, the novel which had itself been plagiarised from Sheridan's book on the Toscan du Plantier murder.

I must admit I hadn't expected that. It was almost breathtaking in its contempt for readers. They were being taken for fools, and she was glorying in the deception.

Who in their right mind would plagiarise a novel that had already been plagiarised? Especially one published by a plagiarist who had been exposed only a few months earlier? Did 'Kate Acton' really think she could get away with it, or did she just relish taking risks?

That it might be the latter was further suggested by some curious details in the book. The character whose murder was copied from the real life case of Sophie Toscan du Plantier is here called 'Isabella English'. The main character in the series which Joanne Clancy copied from my own work was called 'Elizabeth Ireland'.

Isabella is the Spanish and Italian form of Elizabeth. The inverted initials (EI to IE)… English/Ireland - it all seemed too much of a coincidence.

Was 'Acton' symbolically killing the character who had proved to be her downfall? Or, since my name is the Irish variation of Elizabeth and my writing partner is English, was she symbolically killing us? We'd certainly proved to be a nuisance to her.

I immediately emailed 'Kate Acton', who was preparing for a major round of online interviews and other publicity to promote her supposed debut novel.

"Dear Joanne," I said, "I'm sure you know why I'm writing to you. I know what you've done. I know which books you've plagiarised under the pseudonym 'Kate Acton' in Whyte Lies. I think I was extremely generous last time. I'm much less inclined to be reasonable now I've realised you've gone straight back to doing it again. I think we need to meet soon. Please don't bother denying it. It would just insult us both. I said the last time I wanted to hear your side of the story, and that still stands. If you think that by ignoring this email the problem will go away, you're very mistaken. I expect a prompt reply."

I didn't get one.

At this stage, I was growing concerned. Her book was garnering some positive reviews from readers, many of whose names I recognised from the book club, and who would have been horrified to realise that this was the plagiarist Joanne Clancy under a new identity.

She was clearly intent on continuing to sell Whyte Lies, despite knowing that there was little chance of her ever seeing the money, because, once Amazon was alerted to the fact that this book was not an original work, she would be banned again. So I sent her another email.

"When I said I expected a prompt reply, I meant it. If I haven't heard from you by lunchtime tomorrow, I will assume that you have no intention of getting in contact. That's your right but, as I said to you last year, when I first discovered what you were up to, how you respond to me will ultimately determine how I respond to you, and right now I'm not feeling very well disposed towards you. The very least I expected was for you to take the initiative and withdraw your book from sale on Amazon. You must know you're never going to get any money from this scam, yet you're happy to let people carry on buying the book anyway, thereby exacerbating the fraud. Those readers will never get that money back and your choice of action thus far shows total contempt for them."

She didn't reply to that, either. Nor to another one I sent her on July 5. I realised the chances of her replying to anything now were quite slim, though I did think it was quite a risky move on her part. I therefore made the decision to go public with what I knew.

Waiting game

Using the @_ingridblack_ Twitter account I'd set up to promote my own books, I contacted those who'd interacted with 'Kate Acton' and told them that Whyte Lies had been plagiarised, though I didn't say from which sources, as I thought it was up to the wronged authors to decide what to do with the information.

I also put out enough information to make clear that I thought 'Kate Acton' was Joanne Clancy. 'Kate' never replied, but she did remove her books from sale from Amazon and other websites.

Dealing with Amazon proved to be more problematic. As soon as Whyte Lies was published, I contacted the same person in the company that I'd dealt with before. I explained to her that I thought Joanne Clancy was back with a new identity and suggested they take a look at her new novel and examine it for plagiarism. I gave them the details of the two books I knew she'd stolen.

I sat back and waited for Amazon's response.

And waited. Then waited some more.

By now, my complaint had been with them nearly a month, and there'd been no response. I'm not very patient at the best of times, but now I started to get quite irritated at Amazon dragging its heels. I didn't feel that they were taking the problem seriously. I contacted them again.

My one concern was that her account be shut down with immediate effect. Amazon pays out to its authors every two months. If 'Acton''s account remained active, she might receive payment for the books already sold. I was determined that she wouldn't make a cent.

Nothing could have prepared me for the response when it eventually came. Amazon would not be shutting down 'Kate Acton''s account, they declared, because they could find no evidence of plagiarism in Whyte Lies.

They'd run the novel through their plagiarism programs and nothing had been flagged up as problematic.

I was speechless, not to say incensed. I asked: "Did you give it to an actual person to look at?"

No, they replied, nor were they going to. If I wanted to show them that 'Kate Acton' had plagiarised real authors' works, then it was up to me to bring her to book.

These were not, to my eyes, the actions of a company determined to stamp out plagiarism. I'd already proved once before that they were selling plagiarised work. Now I was telling them it had happened again. Did the fact that I was right the last time count for nothing?

Somebody else might, understandably, have refused to do Amazon's job for them; but I couldn't let it go. I undertook to go through 'Acton''s novel page by page, and pinpoint the exact instances of plagiarism. An entire weekend was lost as I compiled a Plagiarism For Dummies report on where this serial faker had stolen from Michael Sheridan's Death In December.

Some of the copying was so inept as to be almost comic. 'Kate Acton''s book is set in high summer, but she forgot to change some details, meaning there were still references in her story to "the first frost of the season". Sentence after sentence had been lifted wholesale.

Sheridan wrote of Toscan Du Plantier's nameless killer: "Nothing stirred in the countryside around him ... he was an animal on the hunt." In Whyte Lies this becomes: "Nothing moved in the countryside around him ... he was an animal on the hunt."

Sheridan's "a halo of blood had soaked into the ground around her head" became Acton's "a halo of blood soaked into the ground around her head." Both books described the area as one "associated with beauty, generosity and hospitality" now being "portrayed as a wild savage place where innocent people were not safe", and the murder itself as "a personal affront to their reputation and the betrayal of the trust that their guests had placed in them." Line after line, paragraph by paragraph revealed the same word-thievery.

I didn't have time to go through The Perfect Crime as well, but I knew that, if I could at least make them see that she'd plagiarised one book, that would be enough to shut her down.

I sent the report to Amazon at the start of the next week. Part of me worried that it wouldn't be enough, that they were so stubborn they'd still deny the evidence even when it was right there before their eyes. At the same time, I knew I was being silly. It was obvious, blatant, undeniable. They had to admit the truth.

They did. They replied to say that 'Kate Acton''s account had been shut down with immediate effect, and seemed to think that they had done a grand job altogether, though in truth they'd done nothing. I'd done all the work, and 'Kate Acton' had managed to effortlessly, contemptuously bypass every safeguard that they purported to have in place to catch plagiarists.

I asked what they intended to do to beef up their checks. Nothing, was the astonishing answer I got.

I asked for more information on 'Kate Acton'. Every author needs to link to a bank account in order to publish a book on Amazon. It's not easy to set up a fake bank account, and I had no reason to assume that 'Acton'/Clancy would do such a thing anyway, so I assumed the bank account connected to 'Acton''s account would be the same one linked to Clancy's account.

There was another issue, too. Authors must provide a tax-reference number to publish through Amazon. So was 'Kate Acton' using the same details as Clancy, and, if so, how had this link not been flagged up previously, considering that she was supposed to be banned for life?

After sending a number of queries to Amazon, I received a reply from Mackenzie Smith, who was described as the director of Kindle. Addressing me as "Ellis" (sic), the email assured me that "we do not want any form of plagiarism on our service and we work continually to improve our systems, both automated and manual, to catch every instance", insisting: "We hear your frustration and have had a number of teams and senior leaders at Kindle looking at the issues you raised."

He also promised to "reach out to Michael Sheridan's publisher about the concerns you raised".

That was last August. As of March this year, the O'Brien Press says it has had no communication on the issue from Amazon. It was left to me to alert the publishers that their author's work had been stolen, which is a woeful state of affairs, but what can I do?

Since then, nothing has been heard from 'Kate Acton', but I have no doubt that Joanne Clancy will be back again. On November 5, 2015, she was writing to tell me how sorry she was for stealing my work. Within six weeks, she was back with a new identity, announcing her intention to write another novel.

Had I been satisfied that Whyte Lies was all her own work, I wouldn't have revealed her identity. Everyone deserves a second chance. The fact that it wasn't, and that 'Acton'/Clancy was so shameless in what she was doing, proved to me that she had no intention of changing her ways, and indeed had probably been stealing other people's work all along. Has she written a single thing that she can call her own? I doubt it.

That's why I'm sure she will return. She may have already. She's not an aspiring author who strayed off the right path. She's a thief who steals others' hard-won words and turns them into money, rather than just taking the cash from the victim directly. It's all the same in the end.

She's got much more defiant in the interim, too. On being exposed last time, she immediately deleted her Twitter account. This time @KCActon is still there. There have been no new posts since her ignominious exposure, but it shows no signs of going away.

Next time, I suspect she may come back as a man, adopt a different nationality, or find more obscure books to plagiarise. Next time, I may not catch her. Thwarting book thieves is time-consuming, emotionally exhausting work. But someone will.

It certainly can't be left to a large company such as Amazon or a computer program, because the former do not care enough and the latter don't catch enough. The fact is that every plagiarist who has been exposed so far has been found out by an ordinary human reader.

Plagiarists can sneak past every defence, but there's no substitute for an eagle eye. Joanne Clancy, or 'Kate Acton', or whatever she chooses to call herself, has been caught red-handed twice now. To borrow a phrase from Oscar Wilde: once is a misfortune, twice is carelessness, and third would be pushing your luck too far.

I now know I made a mistake in letting her off the hook the first time. I won't be making the same mistake again.

Sunday Indo Life Magazine