A banker who had fallen out with his family stipulated in his will that his fortune should only pass to the person in possession of the five keys he distributed to his relatives during his lifetime 80 years after his death. Only with all five keys can the cassette in the vault of a bank be opened, granting access to the deceased's assets. 75 years after the banker's death, the fugitive crook Murphy comes into possession of one of the keys, together with a list of the names of the owners of the four remaining keys. Over the next five years, he manages to obtain two more keys by criminal means. Now he just has to get the fourth key from Carlo and the fifth key from the young, rich widow Maria. Any means will do. But the unscrupulous villain has not reckoned with Carlo's shrewdness, who initially falls under suspicion himself, but then takes up the pursuit of the criminal.

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