Jim McLain (John Wayne) and his partner, Mal Baxter (James Arness), are investigators for the House Un-American Activities Committee, who are sent to Hawaii to find the leaders of a local Communist Party. They visit Dr. Gelster (Gayne Whitman), a psychiatrist who is treating one of the party members. While there, McLain charms the doctor's secretary, Nancy Vallon (Nancy Olson), and asks her out. As their hunt continues, McLain and Baxter become targets of Communist boss Sturak (Alan Napier).