Dave (Nick Thune), who considers himself an artist despite having never completed anything significant in his career, builds a cardboard maze in his living room but gets trapped inside. When his girlfriend Annie (Meera Rohit Kumbhani) comes home and finds him stuck inside, she finds it hard to believe, even though he claims it's much bigger inside than it appears.

Skeptical, she gets a bunch of their oddball friends together to go on a rescue mission inside the maze. To her surprise, the space inside is actually huge and they wind up lost themselves in a fantasy world complete with a bloodthirsty Minotaur, hand puppets who are self-moving and booby traps.