This is a story about a young man named Jason.

About 20 years ago, Jason Callahan went missing. He moved out of where he was living, mystifying his roommates — it seemed like he just up and disappeared. And they never heard anything else about him. The only thing he left behind was phone charges for some 1-900 numbers that were hotlines for Grateful Dead fans.

Across the world in Queensland, Australia, Redditor Layla Betts, who's now 28, started getting into unsolved mysteries. Really, really into them. She stumbled across a Virginia case from 1995, where two men were killed in a car crash. One man was identified, but the other wasn't. He was wearing a Grateful Dead t-shirt and had Grateful Dead ticket stubs in his pocket. He became known as the "Grateful Doe."

Layla posted the story on Reddit:

Layla helped create the subreddit r/GratefulDoe, which was devoted to solving the case. Thousands of people joined in, and Layla says she would sometimes spend 12 hours a day moderating the community — replying to comments, contacting law enforcement, and posting updates. One of those updates was a set of composite sketches of the Grateful Doe.

That post resulted in a message in Layla's Reddit inbox from a guy named Steve. Steve said he recognized the guy in the composite sketches. He thought it looked like one of his old roommates from Illinois — a guy named Jason Callahan.

The next step? Find Jason Callahan's family to confirm. Eventually, those sketches reached Shannon Callahan, Jason's half-sister.

"I honestly started shaking," Shannon told Ben and Amory. "When I looked at that picture, it looked like my dad was looking back at me. He had the same face. And he even had a lot of my facial features — my forehead and the shape of my face. I knew in that moment, deep down, that that was [Jason]."

Shannon offered to take a DNA test. Then she, Layla, and thousands of other online sleuths who were deeply invested in the Grateful Doe case, waited a year for the results.

"Once they came in, it was insane," Shannon says.

The Grateful Doe was Jason Callahan. Case closed.

"It was a very sobering moment," says r/GratefulDoe co-founder Layla Betts. "Because at that moment, it wasn't that this case had been solved after 20 years. It was that Jason Callahan was finally going to go home. His family had a resolution."

The Grateful Doe subreddit still exists. Now that its namesake case has been solved, the community features other missing persons cases — several of which have also been solved.

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Thanks to /u/zettabeast for this week's artwork, "Unmarked Grave." See more at http://www.beyondtheomni.com.