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.
