In 1938 Los Angeles, two gangsters in Eddie Valentine's gang steal a rocket pack from Howard Hughes. During their escape from the authorities that ends up on an airfield, one gangster is killed, the getaway driver hides the rocket pack, and stunt pilot Cliff Secord's Gee Bee racer is destroyed in the resulting auto-airplane accident, crippling his career. Cliff and airplane mechanic Peevy later find the rocket pack hidden inside a biplane cockpit. Movie star Neville Sinclair had hired Valentine's gang to steal the rocket pack, and he sends his monstrous, yet skilled henchman Lothar to question the injured getaway driver, who tells him about his hiding the rocket pack at the airfield.