Two lighthouse keepers (the father and the son) are to spend one entire month in the middle of the sea near the coasts of Brittany;a series of bizarre flashbacks reveals us that the young man has been bitten by a rabid dog.He remembers things of his past,his fiancee,the attack of the dog -which he did not take seriously- and he's seeing things too ,sometimes his visions become mad .As his condition gets worse,he and his father,prisoners of their islet ,inaccessible because of the raging sea ,begin to panic.