Dr. Robert Ordway, Warner Baxter, a renowned psychiatrist and criminologist known as the Crime Doctor, is summoned to an emergency at a party held at his next-door neighbor’s home. There, Walter Foster, George Meeker a guest at the gathering, suffers a diabetic seizure and collapses. Ordway administers insulin to the man, drawing on his medical instincts, but soon after the injection the guest dies, sparking a sense that something deeper is at play.
To unravel the mystery, Ordway enlists the help of the local homicide inspector, Charles D. Brown, who leads the investigation and quickly concludes that the death was the result of poisoning. With his keen observation and medical background, Ordway becomes a key consultant, and the two men begin to sift through the guest list, looking for anyone who might have motive, opportunity, or access to the toxic secret behind Walter’s death.
The first person Ordway questions is Claire Foster, Adele Roberts — Walter Foster’s sister — who claims she has no idea what her brother meant by the troubling line he spoke before he died: "I've given you one face." This cryptic clue becomes a thread that pulls Ordway deeper into a tangle of relationships and grievances at the party. Claire’s own life appears to be bound up with secrets, and Ordway senses that nothing at the gathering is quite as it seems.
Claire’s confidant is her lover, Jack Swayne, Craig Reynolds, the owner of a health institute. He reveals that Walter and Jack were not on good terms, particularly because Walter opposed a marriage that would tie Walter to Jack’s ambitions. Jack further explains that Walter had carried financial burdens, and Ordway begins to trace the traces of money and debt among the guests. A visit to Walter’s attorney, Allen S. Tobin, Charles Arnt, uncovers further financial details: Walter had drained much of his inheritance and was eager to borrow more from his sister to stay afloat.
A frantic phone call from Claire prompts Ordway to hurry to her apartment, only to find it empty and to learn that Claire has been abducted by a man named Casper. The investigation widens as Ordway learns from Harriet, a neighbor who has her own complicated history with Walter, that Harriet and her husband are preparing to move or divorce, a decision tied to the strange atmosphere surrounding the house since the murder. Alec Girard, Wilton Graff — the real estate agent — corroborates that the couple is selling the property, hinting at concealed tensions and possible motives tied to Walter’s life.
Casper’s pursuit leads Ordway to Connie Day, a mortuary worker played by Peggy Converse who becomes a focal point in the case. Casper suspects Connie of involvement in a blackmail scheme targeting the mortuary’s owner, Karl Ganss, played by Martin Kosleck. When Connie is locked inside her office by a colleague, Casper confronts Ordway, and a shocking turn occurs: Casper’s accomplice Louie (uncredited) shoots Ordway, plunging the investigation into a more personal danger as Ordway’s vision is temporarily impaired, and Louie subsequently dies after being pushed out a window.
With his sight returning, Ordway searches criminal records and discovers that a plastic surgeon could have altered a suspect’s face, matching a signature he obtained from Casper to Gypsy Corsello—an infamous criminal who reportedly engineered such reconfigurations. Posing as the criminal Pete Hastings, Ordway infiltrates Gypsy’s circle to uncover the truth and moves to the mortuary once more, where Ganns resists and tries to poison him. A struggle ensues, and the authorities arrive to arrest both Ganns and Gypsy.
Tragically, Claire Foster and Connie Day are found dead in their respective locations, while the mastermind behind the operation—the plastic surgeon who has eluded capture—remains at large. The remaining suspects are invited to a final party at Ordway’s home, where the detective maintains the illusion of blindness to coax out the culprit. After most guests depart, Alec Girard returns, claiming he forgot his glasses and slipping a poisoned drink to Ordway as he explains Walter’s downfall and Girard’s motive: Walter had knowledge of Girard’s past as a surgeon and had begun blackmailing him.
Unbeknownst to Girard, the police are listening in on the confrontation next door, and the moment Girard finishes his confession, they burst in to arrest him. The key threat to Ordway’s life is neutralized only after the poison is flushed from his system, leaving the case closed but with the shadow of the crime doctor’s expertise lingering over the truth Ati the heart of a house filled with secrets, substitutions, and faces that hide more than they reveal.
