In 1944, a group of POW's are working to build trenches along the French coast in preparation from the impending D-Day attacks. But when an unexpected aerial attack arrives, they are forced to seek shelter deep inside a Blockhouse - a giant underground storage facility packed with frontline supplies and hidden Nazi treasures. When the heavy bombardment causes the entrance walls to collapse, the seven men are trapped within and forced deeper into the vast underground chamber. The prisoners are at first buoyed by their discovery of almost limitless wine, candles and rations. But when it becomes clear there is no hope of escape, their physical comfort begins to gives way to a risk of mental disintegration that will provide these hardened soldiers with their toughest test of the war so far.