A traumatized school shooting survivor falls in with a group of students celebrating graduation in a Cold War bunker turned museum, only to find themselves trapped inside with a relentless killer intent on teaching them one final lesson.

It's Alex's 21st Birthday, but she's stuck at the amusement arcade on a late shift so her friends decide to surprise her, but a masked killer dressed as Mickey Mouse decides to play a game of his own with them which she must survive.