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.