Guy buys a Majora's Mask N64 cartridge at a yard sale from this old man. He goes home and plays it, and creepy shit happens with the game. You have to read it, because it's basically a series of separate events that can't really be explained in tl;dr. Link dies a lot, and some creepy messages are displayed a few times ("you shouldn't have done that," "you've met with a terrible fate, haven't you?" etc.)
The story continues with BEN (the name attributed to a file already saved on there) coming out of the game and haunting the guy's computer.