In the summer of 1982, five friends discover an ancient stone box hidden deep in the woods. They seal inside of it treasured objects from their childhoods, and they make a vow:

Never come to the box alone. 
Never open it after dark. 
Never take back your sacrifice. 

Four years later, a series of strange and terrifying events begin to unfold: mirrors inexplicably shattering, inanimate beings coming to life, otherworldly crows thirsting for blood. Someone broke the rules of the box, and now everyone has to pay.

But how much are they willing to sacrifice?