When a teacher is found dead, having apparently committed suicide, his friend Pierre Hoffman takes over class 4F and finds himself responsible for a group of strangely subdued, well-behaved and yet menacing pupils.

Assuming their behaviour to be a response to the trauma of their teacher's death, Pierre Hoffman at first takes it easy with the precocious class, refusing to embrace the hostility felt by other staff members towards the children. Over the weeks that follow, however, he receives a series of signals and warnings that cause him to question the motivations of his pupils and the circumstances of his colleague's suicide.

Refusing to believe that the situation can be any more sinister than his suspicious imagination, Hoffman applauds and supports class 4F's decision to organise a school trip to the Normandy coast. Only once the trip has begun, however, does Hoffman begin to understand the extent of their bizarre solidarity and their ultimate goal...