時は明治十一年。急速な欧米化に伴い、政府に不満を持つ人々が増え、監獄は囚人で埋まり、脱獄も後を絶たなかった。そこで政府は、滋賀県琵琶湖に重犯罪者専用の檻、日本最大・脱出不可能な湖の監獄、獄門処を設ける。その監獄への橋渡し人を請け負う曇家の三兄弟が織り成す大冒険活劇の幕が上がる……!。When he learns his days are numbered old count Hervé de Kéraudren decides to hide in a secret alcove and to die there, just to annoy his heirs. As a result of his body not being found the latter will have to wait for five years until they can inherit the count's money. Very upsetting indeed, all the more as they are required to keep up the Kéraudren estate in the meantime. To collect money, nephews and nieces organize a Son et Lumière show at the manor while busily looking for the missing corpse. But, unexpectedly, they get killed in turns. Murders or accidents? Jean-Marie, his fiancée Micheline and his cousin Edwige investigate and finally succeed in exposing the culprit. And, the count's body being found by chance, all goes back to normal.。一对夫妇雇了一名妇女来照顾他们残疾的儿子。在注意到看护者奥利维亚的一些奇怪行为后,母亲决定仔细观察。奥利维亚的黑暗过去浮出水面,危及所有与她接触的人。。