Based on

Movies like Seven Keys (1961)

Convict Russell is bequeathed a set of seven keys by a fellow prisoner. After discovering that the deceased was an embezzler who stole an unrecovered £20,000, he sets out to find the cash after finishing the last three months of his sentence. However, he must first solve the mystery of which locks the keys fit, and run the gauntlet of the police and a number of gangsters who are after him and the money.