[1][2] His portion of the loot from a recent heist squandered, minor-league criminal Frank Harper talks his boss, Flood, into a more lucrative project: on the weekend before a Monday payday, break into a San Felipe, California bank, which will be holding a million-dollar payroll for the Marine Base at Camp Pendleton.

Flood plans the operation, sending his moll Kay with Frank to become established in the community at San Felipe and to lay the groundwork for the heist.

During their stay in the neighborhood, Frank and Kay establish a friendly relationship with the Loxleys'; husband Sam is a banker.

Flood goes over the final plans for the robbery, in which Zimmer is to create several explosions, including one at the high school as well as one at the electric power plant (thus disabling the bank vault's alarm system).

On the night of the robbery, Frank and Kay attend an evening barbecue at the Loxleys', and hear over the radio about the discovery of a young woman's body.

Later, after Flood returns to Frank's house with cases full of cash, Frank knocks him unconscious and tells Kay to phone the police, intending to return the cash, assuring Kay that, no matter what criminal charges they may face, somehow they will find a way to be together.

[3] Film rights were bought by Pine-Thomas Productions who had renamed themselves as Pine-Thomas-Shane following the death of co-founder William Pine.

The setting of the novel is the fictional town of "Indio Beach," described as between Palm Beach and Jacksonville on Florida's west coast;[6] whereas the film adaptation places the action in the fictitious California coastal town of "San Felipe," portrayed onscreen as neighboring Oceanside and Camp Pendleton.

According to a Hollywood Reporter news item, The Big Caper marked the first time that Ates, who had appeared in dozens of films, did not use his signature onscreen stammer.