1917. The Western Front. It is here that one young man must face the truth about himself: that he is a coward, unable to face the coming horror of battle. Private Charlie Shakespeare (Jamie Bell) is frozen with fear. Forced over the top at gunpoint, he is hurled into the chaos of battle and witness to the decimation of his comrades. He is alone, desperate to turn and flee. Then the poison gas drifts over the nightmare battle field and all he can do is fumble for his mask, press himself deeper into the mud and pray for dawn... When the battle is over, Shakespeare and the handful of other survivors take shelter is an abandoned German trench, waiting to be rescued. But no-one will come and as the night draws in, one by one, the young men of Y Company begin to die. An unseen enemy is stalking them, driving them insane with fear until they begin to turn on each other. Is their refuge possessed by something even more terrible than the war that surrounds them?