Nan Lowry Collins, Laraine Day, has just married Brad Collins, Robert Ryan, a San Francisco shipping executive who once worked as a stevedore in New York and clawed his way up to vice president of a respected firm after a whirlwind one-week courtship. On their honeymoon, the couple encounters Christine Norman, Janis Carter, Brad’s old flame who instantly rubs Nan the wrong way.
Brad’s hard-won career, built from the docks to the boardroom, draws the attention of a hidden Communist cell led by Vanning, Thomas Gomez. The group makes a brutal example of an FBI informer to show the stakes, and Vanning threatens to expose Brad’s true name, Frank Johnson, along with the possibility of responsibility for past political violence. To neutralize him, the cell orders Brad to undermine labor negotiations in the Bay Area by stifling union demands, insisting that withdrawal from the party is not an option.
Christine Norman, a tool in Vanning’s plan, is told to draw Brad’s brother-in-law, Don Lowry, John Agar, closer and to steer him toward a Communist worldview. Christine’s loyalty wavers, though, as she falls for Don, even as Vanning presses for restraint and obedience. The tension deepens as Jim Travers, Richard Rober, a friend of Nan and a principled union leader, cannot reconcile Brad’s increasingly erratic stance with the values he once shared, and he worries about a small but ruthless faction potentially taking control of the union.
When Nan learns of her husband’s clandestine past, she confronts Christine and discovers the full extent of the manipulation. Christine unveils, too late, that Bailey, William Talman, the henchman involved in the earlier hit, was responsible for Don Lowry’s death. In a charged moment, Christine begins a suicide note to reveal everything, but Vanning interrupts and destroys her confession, ordering her to vanish from the apartment window.
Driven to uncover the truth, Nan adopts a bold ruse of her own: she pretends to seek a killer for hire to eliminate her husband. The trap is sprung when Nan is abducted and brought to the Communist headquarters along the waterfront. Brad tracks her down and bursts into the scene, and a tense shootout erupts. In the end, Bailey and Vanning are killed, and Brad is fatally wounded.
In his dying moments, Brad attributes Nan’s past happiness to Travers, suggesting he was the right man for her all along. Nan cradles Brad as he passes, the memory of their conflicted, perilous romance lingering as she contends with the truth she’s uncovered and the love that remains.
