The undercover cop stung Mark Franklin at his weakest. It was October 2010, and Franklin had just returned to Rarotonga from Auckland Hospital, where doctors dropped the bombshell that he had throat cancer.

The former detective inspector was working for Cook Islands police on serious fraud and corruption cases at the time, while also playing in a band at resorts and bars on the island.

Around the time of the cancer diagnosis, Franklin was playing at Trader Jack's, the legendary bar next to Avarua Harbour, when he was approached by a man who said he was a former Counties Manukau police officer, the same district Franklin had spent the early part of his 27-year career.

The man, from a prominent Cook Islands family, was super-friendly, buying drinks for Franklin and the other members of his band, Nocturnal Habitz. Unbeknown to Franklin, his new friend had recently been sworn in to the Cook Islands police and was their main weapon in Operation Eagle, a joint investigation by local and New Zealand police into cannabis dealers.

Franklin takes up the story from Rarotonga's Arorangi Prison, where the Sunday Star-Times visited him last weekend.

"He started weaving this story. He said he was involved in the law enforcement team in South Auckland and that he was involved in policing cannabis. He told me he'd been suspended and he suggested it was because of some cannabis [use] himself.

"I actually considered that he could be [undercover] but given that I knew he was an ex-cop, I knew his dad and his brother - I just couldn't see it."

Over the next few weeks the officer turned up at various bars Franklin was playing at - always buying the drinks - and according to Franklin, began "pestering" him for cannabis, saying he needed it to impress some "hot" Dutch backpackers with whom he was hoping to have sex. He would also turn up at Franklin's house uninvited. It turned out later he was wearing a wire.

"He said, ‘Mate, a lot of the boys back home smoke a bit of dope and drink a lot of piss as a way of dealing with stress. I don't see anything wrong with it.' "

Franklin says he fobbed the man off, but one night in late November, "caved in". He was playing at Trader Jack's when a woman who supplied him with his cannabis walked in.

Franklin took two $50 notes from the undercover officer, approached the woman (who is now locked up in prison with Franklin) and she gave him two small packages of cannabis, which he gave to the officer.

He then returned to New Zealand for seven weeks of radiation and chemotherapy, losing 25kg, and used cannabis on his return to Rarotonga to help with nausea.

The following April, Franklin says, the undercover officer began pestering him again. Franklin says he resisted for a while, but wanted to get the man "off my back" so bought two small packages of cannabis for himself and two for his "friend". The drugs were handed over underneath Franklin's house in Nikao, northwest Rarotonga, for $100.

One of Franklin's bandmates, Alby Marsh, says the undercover officer seemed suspicious because he constantly tailed the band around wanting to buy weed. "I said to the guys, ‘don't talk to him, for all we know, he could be a pig'. He was just trying to earn some stripes."

In May 2011, police officers with drug dogs stormed Franklin's home.

"I knew what it was as soon as they came in the door."

If he thought his colleagues in Cook Islands police might go easy on him, he was mistaken. He was kept in police cells for a couple of days, denied visitors or international phone calls, and was remanded to prison for two weeks, before getting bail so he could return to New Zealand for medical treatment.

His name was suppressed, but that didn't stop New Zealand media naming him.

"What really hurt me was the fact there was a name suppression order but I didn't have the chance to tell anyone, and of course there's my mother and my sister and my daughter [in New Zealand] all watching it on One News, that was the first they knew."

Media coverage referred to a "major drug ring" and the biggest operation in Cook Islands history. Franklin says the amounts of cannabis involved were small and, apart from the woman who supplied his cannabis, he didn't know the other 11 people who were arrested.

"The media attention in New Zealand was ‘top homicide detective biggest drug boss in Cook Islands' - which is not me at all."

He says those arrested as part of Operation Eagle were mostly social cannabis users - the top tier of importers and suppliers were ignored, despite large amounts of money and resources being thrown at the investigation.

Franklin's legal team looked at entrapment as a possible defence, but the threshold was too high and it was decided pleading guilty would be better, although that backfired when the Cook Islands' draconian drug laws kicked in and visiting New Zealand judge Colin Doherty gave him a year behind bars.

The undercover officer also stung others, including his best friend from school, Giovanni Marsters, son of then deputy prime minister Tom Marsters. Giovanni is now doing a six-year lag.

Franklin says a lot of people in Rarotonga are upset with the officer, and he doubts he could show his face on the island again.

"He's made the decision to come here and . . . betray the local community. He's targeted his old school friends, he's told lies, deceived people."

The last time Franklin saw the man was at Trader Jack's about a month before he was arrested, just as the officer was about to return to New Zealand.

"He wouldnt even look at me. It was then I realised ‘he's an undercover cop'. It was too late by then. You could see his face, he was distraught, you could see it going through his head, what he'd done."

ISLAND TIME

Franklin mingles with other prisoners in a courtyard at the front of the jail, waiting for visiting time. Chemotherapy, surgery and a 30-a-day smoking habit (now kicked) have made him a shrunken version of his former self.

Today he is hobbling because of gout, and seems much older than 54. "Have you got any Voltaren," he yells to his girlfriend, Vaine. She heads off to find him some.

At noon a guard unlocks the gate, and prisoners file out. For the next two hours, they sit with their families at picnic tables, chatting over lunch, while guards watch lazily from a distance, sometimes turning their backs or disappearing altogether.

It would be a simple thing to run off, but there's nowhere to go, so no one bothers. A man wanders over to shake Franklin's hand - it's Tom Marsters, now the Queen's Representative for the Cook Islands, who's here visiting his disgraced son.

In some ways it's inevitable that Franklin ended up here, since he dabbled with drugs for many years.

"I joined the police [in 1978] and I wanted action straight away and got posted to South Auckland. I just threw myself into it and I gave the police all I had. It didn't take long before I realised it was affecting my health quite badly.

"One of the things I did to try and combat that was to smoke a bit of cannabis. It's probably something I shouldn't have done but it was always at home in the evenings, with my own friends away from the police."

Franklin says he first realised the stress of policing was getting to him when he couldn't make his 2-year-old daughter's birthday because he was watching an autopsy.

Then came Delcelia Witika, the 2-year-old tortured and killed by her mother and stepfather in South Auckland in 1991.

"I was OK during the investigation, but when the trial finished I just broke down."

Around 1998, Franklin was leading the reopened investigation into the 1989 murders of Deane Fuller-Sandys and Leah Stephens. Former Black Power enforcer Stephen Stone had made a roomful of witnesses pump bullets into Fuller-Sandys and then a week later raped and murdered Stephens because he was worried she would nark.

"That was one of the most difficult investigations I ever did, it lasted for two years, the stress was huge and I was carrying that."

During the investigation, Franklin and some friends were in downtown Auckland on a Friday night, walking down an alley passing around a joint, when they chanced upon some police officers who knew Franklin. It was an embarrassing moment.

No arrests were made, but Franklin felt bad about putting the officers in a predicament, so approached his supervisor on Monday morning to clear the air. "All that came to nothing, I think it was a warning and that was it."

The homicides just kept coming, especially when Franklin moved to West Auckland. Next up was Marie Jamieson, the hairdresser who was abducted off the street, stabbed to death and dumped behind a warehouse in Ranui.

"After Stone, that was a double whammy, I was pretty hard hit by then."

Franklin says he visited a police psychologist three times, and told him about his cannabis use. "It's not as if I wasn't trying to deal with the issue."

He doesn't believed he was addicted. "It's more a psychological thing. I found it very relaxing and, contrary to some people, I found it very motivating. In the evening you could sit there and reflect on things and find the next morning you were focused."

It troubled him that he was breaking the law, "but I felt like I was doing a great job, giving it 120 per cent and getting good results".

Franklin became crime manager for Northland and, in 2004, was seconded to the Cook Islands to review an historic homicide. He loved the place, and decided to make it his new home. Having been diagnosed with post traumatic stress disorder, he was able to "Perf" from the police, or take early retirement on psychological grounds.

He headed to his island getaway, ready to start a new life.

CALL OF POLICE BECKONS AGAIN

Franklin had intended to focus on his music, but the call of police work beckoned once again, and he took up a contract to mentor and train local police, as well as lead serious fraud and corruption cases.

"It was the wrong thing to do, the trauma and the stress continued because I was still in a police environment."

Again, to relieve the stress, he turned to cannabis, which at $50 a tinnie was almost three times more expensive than New Zealand. Franklin knew a couple of people who sold weed, most of it brought in from New Zealand. His lawyer, Tony Manarangi, says there is some dope on the island, but not in huge quantities. "It's all social stuff, I've never known a Mr Asia to be here."

Manarangi says the suggestion Franklin was some kind of Mr Big is ridiculous. "He's very embarrassed that everyone thinks he's a dope dealer; you wouldn't have a worse dope dealer on the planet."

In the end it was Franklin's work investigating corruption in the Cook Islands that led to his downfall. He led a two-year investigation that resulted in charges against MP Norman George, a lawyer who Franklin suspects was tipped off that he was a social cannabis user.

"He tried to get me chucked off the investigation by making allegations of me being a drug dealer. That's where it all started, it was a personal attack on me."

In some ways, being charged was a big relief, as it meant there would be no more policing, no more stress.

Franklin has been in prison for almost a month, and says it's not too bad. No one wants to have a go at him because he's a cop. He's teaching other prisoners to read, write and play guitar and has started a prison band.

He says getting up at first light for cell inspections and early to bed is just like being back at police college.

He has appealed his sentence and hopes to be out in eight months on parole. He just wants to do his time, and then get back to his music. His cancer is in remission, and he has plans for an entertainment business.

Franklin says he is not worried about what people are saying in New Zealand. He remains proud of his service to the community.

"There will be some people who don't like what I've done because cannabis is a drug and drugs are bad.

"But I've got extremely good support from my family and friends, and people I know in police circles generally think that it's been dealt with a bit heavy handedly.

"I feel like I'm taking the flak for Operation Eagle, when I'm just Mark Franklin, a social cannabis smoker."