A chance encounter on the snowy slopes of a castle moat throws together three lonely teenagers: Emily, Simon, and the highly imaginative and enigmatic Marcus.

At first, the castle’s ruins are merely the backdrop to a day in the snow. But when the three break in to the forbidden interior of the keep, they find the castle taking on a different, and deeper, meaning. Despite the freezing conditions, they spend the night there, to experience the power of occupation.

But when the reenactment gets out of control a very real siege ensues, and their playful dare soon turns into a frenzy of nightmarish action