Corporal Larry Grant and Sergeant "Mac" McGowan, of the United States Marine Corps, are rival for the love of Frances Schiller, but team up to hunt down "The Tiger Shark," a mad, scientific wizard who is holding Sergeant William Schiller, Frances' brother, a prisoner on a wild, jungle island in the Pacific.

J. Ward Thomas of Park Avenue leads a double life as an investment broker and as notorious gambler Spade Martin, despite the protests of his beautiful wife Natalie, a nightclub singer who retired when they married. Spade's younger brother "Chick" wires Spade from Seattle that he has quit gambling for a job in real estate and is about to marry a nice girl named Betty. Relieved to find his kid brother is straight, Spade sends him $10,000 cash as a wedding present. When a woman posing as a pregnant wife comes to Spade for a loan, Spade gives it to her. Later, when Steve Burdick, the woman's supposed husband, brags in a bar that he made a fool of Spade, Spade's hit man, Trigger, kills Burdick. Tired of Spade's gambling, Natalie books a return engagement at Cafe Nocturne, telling him that she is a singer rather than a wife now.

A policeman makes the startling discovery that his girlfriend is involved in a waterfront smuggling racket.

In Arizona a young woman who's being manipulated by an evil businessman is helped by the Cisco Kid who happens to be there on holiday.

Young intern Jeff Burton, impulsively offers a lift to an odd-looking gentlemen. It soon turns out that Jeff's passenger is an inventor has just escaped from a shady sanitarium, where he has been held prisoner by Nazi spies.

Eccentric tycoon Jasper Whyte hosts a dinner at his mansion and announces that he will divide his money and give each guest a million dollars before the stroke of midnight. When his long-lost granddaughter suddenly arrives, Whyte changes his mind and proclaims that she will receive his entire fortune. A second lady appears at the estate, claiming that she is actually Whyte's granddaughter, Doris Waverly, and the first woman is found murdered in her room! With each guest possessing a motive, the mystery of the killer's identity briskly unfolds through a stirring series of surprises.