In 2002, 6th Grader Clyde and his friends are introduced to a new substitute teacher named "Mr. Cotard". But this seemingly average week will turn into a nightmare, and will take these students through an experience they will never forget.

Substitute is a Creepypasta series that tells the story of Clyde as he recounts his experience with a strange substitute teacher he had in 6th Grade named Mr. Cotard. What started off as an unusual substitute turned into a living nightmare as Clyde and his friends are taken to the Headquarters of a strange organization called the TTC, whose sole goal is to teach them that everything they know isn't real.