Last week we brought you the story of how a group of online detectives uncovered an elaborate internet cancer hoax that lasted for 11 years. But as they worked to get to the bottom of one hoax, an even more twisted one was right in their midst: now it's been revealed that one of the people involved in the investigation was a woman posing as a teenage boy to prey on an underaged girl.

"J.S. Dirr" ended up being Emily Dirr, a 22-year-old who lived in her father's house in Ohio. James Puryear, one of the sleuths responsible for Emily's undoing, is allegedly a 24-year-old Massachusetts woman named Carissa Hads.

The collision of these two hoaxes starts with "Puryear," a commenter on the Wordpress blog that had launched the investigation into J.S. Dirr, the Canadian policeman who didn't exist. Puryear wasn't particularly notable; he was just another voice in an outraged chorus of people who'd been taken in by the story of J.S. Dirr. For over 10 years, J.S. had lived a vibrant life online, meeting friends and lovers through a half dozen social networks. He and his wife became prominent members of Facebook's pediatric cancer community after their son Eli was diagnosed with cancer. But the sudden death of J.S.'s wife in a freak Mother's Day car crash sparked doubts about his story. Within hours, online sleuths discovered J.S. Dirr was a hoax. Eventually, Emily, a medical school student from Ohio, would admit to inventing J.S. and his entire family—a network of more than 70 fake personas.

But the full extent of the Dirr hoax was only becoming clear when Puryear appeared on May 16, two days after the supposed crash. He claimed to be driven by the fact that he had once tried to send the Dirrs a care package for Eli, and now realized he'd been duped. He began offering theories about the twisted person behind the hoax and digging up evidence, including J.S. Dirr's old Photobucket account.

"Does anyone have screenshots of their pics because you can run it through some websites and see if there maybe are no J.S. and Dana and those pics are stolen," Puryear suggested.

Carissa Hads.

Puryear commented a couple dozen times and when the investigation moved to a private Facebook group, he followed it there. Now, the group of anonymous commenters who had spent hours picking over J.S. Dirr's online life on the Wordpress blog could see each other's real identities for the first time. On Facebook, Puryear was revealed to be "Preacher James Puryear," a single teen dad and aspiring youth pastor. His profile picture showed a scrawny teenage boy scowling in a beanie, with a stud under his lip and a giant tattoo on his right arm: a scroll with "Only God Can Judge Me" wrapping around a cross.

But James Puryear, like J.S. Dirr, never existed. Police now allege that Puryear was the alter ego of Carissa Hads, a 24-year-old woman from Quincy, Mass. Hads, it is now alleged, concocted Puryear in order to have sex with a 15-year-old girl from West Viriginia she'd met on the internet.

According to an affidavit sworn by an investigator with the Internet Crimes Against Children Task Force and posted by the Smoking Gun, Hads met the girl—called "A.L." in court documents—on an unnamed social network in October 2010. (The affidavit refers to the alter ego as "James Puryear Wilson"—Hads had another Facebook account under that name.)

Over the next few months, Hads, posing as "James," plied A.L. with presents, including a Kindle and a cell phone she would later used to send him nude pictures. The two sent care packages back and forth, and shared a notebook in which they took turns leaving messages, creating a single record of their correspondences.

In December 2011, 14 months after they met online, A.L.'s mother drove her daughter to Corapolis, Pa., to meet James in person for the first time. That night, in a motel room paid for by the mother, Hads, posing as James, sexually assaulted A.L., according to the affidavit. A couple of months later, Hads visited A.L. in West Virginia and sexually assaulted her again while staying in her family's home. She used a prosthetic penis during sex, and never got completely undressed, according to the affidavit.

Hads allegedly fooled A.L. and her mother completely, but she didn't have as good luck passing off Puryear to those investigating the Dirr hoax. Soon after Puryear joined the private Facebook group, users grew suspicious. Hours of navigating the labyrinth of fake Facebook profiles and blogs that made up the Dirr family had made everyone involved in the investigation paranoid.

"People started getting a feeling that something wasn't right," said Becky Rogers, one of the members of the Facebook group.

The introduction Puryear had written to the group contained a dozen red flags: exotic illnesses, an unusual backstory:

Hey everyone, I am Puryear. I am 16 years old and I live in Boston. I have aspergers/adhd/bi polar and sensory issues. I also have ms to go along with a broken back and nerve damage. I have twin boys that I love more than anything.. I met "eli" because I make packages for kids that need extra smiles. I make them all the time for kids with cancer who need a pick me up, I donate mp3 players and iPods to autistic kids, help buy toys for families that need, and any other kid that I feel just needs love because they have a disability or struggle through life. [...] My passion is church, I want to be a youth pastor and teach other kids to give back to their community. Also, if any of you know a kid that deserves a package let me know!.

The lack of pictures of both of Puryear's twins together was another troubling sign.

"Something we've learned," Rogers told me recently, "is that if the kids weren't together in pictures, that's a big tip off."

Puryear's Facebook page.

As doubts about Puryear's identity rose, Taryn Wright, the day-trader who spearheaded the Dirr investigation, confronted Puryear on Facebook.

"I don't believe you're a real person, or at least not the real parent of twins," she wrote to Puryear in a private message.

"Uh…? mk well Im sorry u feel that way," he replied. "I suppose you could have talked to my ex gfs mom since she's met me a few times and I stayed at her house…. and Im staying with her in PA for the weekend.. but I understand you being paranoid with everything that has gone on."

On May 22, Puryear was kicked out of the group.

Two days later, on May 24, police arrested Carissa Hads while she was posing as James Puryear in Pennslyvania. She'd told Taryn Wright the truth about heading to Pennyslvania for the weekend, where she thought she was going to meet with A.L. despite the fact they had apparently broken up earlier in the month. When she was arrested, Hads had a prosthetic penis in her pocket and a brace to cover her breasts.

Becky Rogers was scrolling through her Facebook timeline earlier this week when she glanced a news story reporting Carissa Hads' arrest, posted by a local radio station.

"Something made me say, wait a minute, that picture looks familiar and I went back and looked at the picture and said, 'That can't be.'" she said. But after comparing the photos in the news report to pictures Puryear posted to the Facebook group, she knew that the young preacher who'd been so shocked by the Dirr hoax was not who he seemed.

The layers of deception shocked Rogers and the rest of the group. Even as Hads, pretending to be Puryear, was voicing her outrage over the Dirr hoax, she was keeping up a blog where Puryear wrote about his fake twins and his girlfriend, A.L. His fake youth group had a website, just as J.S. Dirr's fake band had one. And Puryear haunted the same cancer Facebook community as J.S. and his wife, leaving comments on numerous "prayer pages" for kids with cancer.

And the revelations threw an unsettling light onto Puryear's contributions to the Dirr investigation. When Emily Dirr, the college student, confessed to creating J.S. Dirr, Puryear offered one theory.

"Maybe she feels like she should really be a boy but cannot tell her family that," she wrote, "so she lies online and makes up a fake person…?"

And at another point, Puryear casually asked about how the Dirr hoax was uncovered.

"How was it found out they were fake?" Puryear asked. "Im young so I don't know what to look for in a fake page or how to find out if they are real or not."

The answer must have chilled Hads, if she'd learned it at the time. In a bizarre coincidence, both the Dirrs' and Puryear's undoings had their roots in pictures of twin sons. The Dirrs' hoax began unraveling when it was discovered that photos of their twin sons were stolen from a popular mommy blogger. And Puryear was unmasked after a friend of A.L. found that pictures of his twin sons were stolen from a photographer's website, according to the affidavit.

In investigating the Dirr hoax, Hads was probably looking for tips on how to keep her own lies under wraps. Instead her very participation showed how impossible that would be.