Brad and Nan Collins, a labor negotiator for a San Francisco shipping company and an interior designer respectively, have just gotten married after knowing each other for only a week, she who was casually seeing his union counterpart, Jim Travis, before meeting Brad, the two men friends despite being on opposite sides of the negotiation table. What Brad has not told Nan is that his real name is Frank Johnson, he having changed it to escape his past as a card carrying Communist. He finds that the Communists are trying to reign him back into the fold when, on their honeymoon, he and Nan run into his old girlfriend, renowned photographer Christine Norman, who is secretly an active Communist agent, she the reason why he joined the Communist Party in the first place. What Brad initially does not know is that the Communists' goal with him is to take specific action in negotiation with the union in order to take control of the shipping industry in San Francisco. Against the directive of her boss Vanning, Christine believes that an insurance policy is to become intimate with Nan's impressionable younger brother, Don Lowry, for who Brad had gotten a job on the docks as a stevedore. These developments will ultimately place Brad, Nan and Don's lives in danger as the Communists will do whatever required, including kill, to reach their goals.
—Huggo