In Ventura, Joan Marshall plays Emily, a mysterious woman who persuades a hotel bellboy to rendezvous with her at a local justice of the peace and marry that night for a fee of $2,000. The ceremony unfolds at the justice’s home in the dead of night, the official is murdered during the act, and Emily slips away. Later, she gloats to Helga Swenson, Eugenie Leontovich as Helga Swenson, the mute, elderly invalid she tends for a wealthy family, about her deed.
Investigators begin a careful, chilling inquiry, discovering that the nurse was given the name of a local flower shop owner, Miriam Webster, Patricia Breslin as Miriam Webster, who has an alibi for the night in question. The case grows more tangled as it’s revealed that Miriam and her brother Warren, who has just returned from Denmark, are heirs to their father’s estate. The old man’s will favored a male heir, reflecting a misogynistic mindset, and Miriam also reveals that she is engaged to Karl, Glenn Corbett as Karl Anderson, signaling how ambition and inheritance intertwine in the family.
That evening, Emily breaks into Miriam’s flower shop and wrecks the place, only to be interrupted by Karl, who did not know Miriam had left earlier. The following day, Miriam and Karl visit Warren’s house to confront Emily and check on Helga. Helga frantically attempts to communicate with Miriam, who later learns from Warren that Emily is actually his wife—hired to care for Helga. Miriam overhears Warren and Emily talking but does not witness them together.
Karl learns of the murdered justice of the peace and that Emily resembles the suspect. Miriam heads to Warren’s residence, where she encounters Helga descending the staircase on a stairlift. As she approaches the bottom, Helga’s severed head falls, shocking Miriam and triggering a fierce confrontation with Emily. In the struggle, Emily removes her wig and prosthetic teeth, revealing herself to be Warren. Warren then tries to kill Miriam, but a police officer enters just in time; Miriam shoots Warren dead.
The police later reveal the full truth: Warren was biologically a girl. The secret of the birth was known only to Helga and the county clerk, who were bribed to record a boy’s birth to avoid the murderous wrath of Warren’s father. Emily was Warren’s overseas alias, created to live as a woman and to conceal the truth. When Warren’s father died, the disguise was revived to kill and silence anyone who might expose the secret.
