A young programmer starts to question reality when he adapts a mad writer's fantasy novel into a video game.

In 1984. Stefan is developing a computer game based on the book 'Bandersnatch', a novel where you get to make choices that determine the story. He has an opportunity to take his game to Tuckersoft, a software company, and have them release it. However, the more he works on the game the more his life emulates the game, with choices being made that are out of his control. Stefan appears to be going insane.—.