In February 2014, a guy named Jason Dang uploaded this photo and said he found the note in a book on a shelf of a café.
The note reads:
Congrats! You have found THE note. I will give you $300 if you come back here on May 27, 2015.
The mystery note writer also left a code word, which Dang covered up.
The note got a lot of attention, and over 1,000 users commented on it. Many users told him it was clear: He had no choice but to go back the next May.
Dang wrote that he put a counteroffer in the book, but never heard back. "I came back in July, (his note) was still in there," he said. "So I took it out and assumed the original date still stood...if they remembered anyways."
In the following months, Reddit users periodically mentioned the note in other threads and asked Dang not to forget to go in May. In January, he posted that he was still planning on going.
"Wow, you guys are really having one hell of a following on this," he wrote. "No worries, I have the date blocked out on my calendar and I'll be there all day (seeing how the person who left the note gave no specific time) lets just hope he holds up his end of the deal."
On Wednesday morning, Dang posted that he got to the café right when it opened, and hung up a sign.
So far, Dang hasn't gotten his $300, but he has gained a ton of followers on Reddit who are watching for his live updates.
Some people think he's about to get killed or robbed.
Others have some more interesting theories.
And of course, some people think it's all an elaborate hoax.
Dang later posted that when he checked another book on the shelf, he found it was full of rocks.
Dang claims the entire saga is totally true. "I have no reason to lie to anyone," he told BuzzFeed News.
Regardless of what is really happening, Dang still ended up ahead. He said a Reddit user approached him and gave him $10, and so far he's spent less than $6 at the cafe.
As the hours passed, other Reddit users began to send Dang food and presents in support of his quest. He wrote that he had gotten at least three pizzas delivered to the cafe.
He got fan mail, including gift cards to the cafe.
A website called ScrewAttack hooked him up with a bunch of stuff.
And he got his $300! Well, not really.
Pretty soon, a bunch of local Reddit users came out to party with him at the cafe.
The note creator never showed up. But Dang wrote it turned out to be a pretty great day. And, he finally revealed the secret code:
Dang said that in the end, "the $300 that was promised was nothing compared to the entire experience as a whole."
"All the awesome loot that was given out, and all the people I met and came in contact with, in person and online, made the whole worth all the while," he told BuzzFeed News.