Francis Ingram (Victor Francen) is a noted pianist who lives in a large manor house near a small, isolated Italian village. Ingram suffered a stroke which left his right side immobile, and he has to use a wheelchair to get around. He has retreated to the manor house for the past few years—seen by only a few close friends. These include his nurse, Julie Holden (Andrea King); a musicologist (and amateur astrologist), Hillary Cummins (Peter Lorre); a friend, Bruce Conrad (Robert Alda); and his sister's son, Donald Arlington (John Alvin). Ingram has fallen in love with Julie Holden, and has changed his will so that she receives the vast bulk of his enormous estate when he dies. But Julie is secretly in love with Conrad. The change in the will disinherits Arlington and Cummins, and Cummins tries to expose Holden's affair. Ingram, outraged at the slander on his beloved's good name, tries to choke Cummins to death. Only Julie's arrival (after meeting Conrad in the garden) saves him.
Later that night, Ingram begins to suffer hallucinations from poison put in his food and drink. He climbs into his wheelchair, makes it to the top of the stairs, and calls out for Julie (who never comes to his aid). Ingram falls down the stairs, breaking his neck. (The audience does not see if Ingram was pushed or he fell.) Commissario Ovidio Castanio (J. Carrol Naish) of the local police investigates the death, but finds little sign of murder.
A few days later, Raymond Arlington (Charles Dingle) (Donald's father) arrives, determined to ensure that his son gets the inheritance. Duprex (David Hoffman), Ingram's attorney, tells Raymond that there are suspicions regarding Ingram's death that may lead to overturning the new will in favor of the old one. That night, Duprex is murdered by an unseen assailant. Commissario Castanio begins to investigate. The Arlingtons try to search for the old will, while suspicion falls on Cummins after he tries to remove several expensive old books from the manor house. That night, everyone hears Ingram playing the piano in the main hall, but when they go to check no one is there. Donald, too, is attacked and almost choked to death. Commissario Castanio discovers that someone has broken into the Ingram mausoleum and cut off Ingram's left hand. But it seems impossible for anyone to have gotten in or out.
The audience now begins to see a disembodied hand moving around the manor house. The hand attacks Cummins, but he is able to assuage the hand's quest for vengeance by giving the hand Ingram's signet ring. He locks the hand in a closet, but when Conrad and Holden appear to see what has happened — the hand has disappeared. Meanwhile, Donald Arlington remembers the combination and location of an old safe in the house, and Commissario Castanio and his father accompany him to the room where it is located. They discover the old will...and the disembodied hand. In a fit of madness, Donald Arlington flees the house with Conrad in pursuit. He comes to his senses, and is not harmed. When Holden claims to have discovered the hand, Cummins (becoming more and more mentally unhinged) tries to burn it in the fire. But the hand crawls out and chokes him to death.
Commissario Castanio discovers a hidden record player and concludes that Cummins was playing it to scare people. He theorizes that Cummins cut off the hand, killed Duprex, and tried to kill Arlington. By which point, his mind had snapped, making him believe his own fabricated plot.Robert Alda as Bruce Conrad
Andrea King as Julie Holden
Peter Lorre as Hilary Cummins
Victor Francen as Francis Ingram
J. Carrol Naish as Commissario Ovidio Castanio
Charles Dingle as Raymond Arlington
John Alvin as Donald Arlington
David Hoffman as Duprex
Barbara Brown as Mrs. Miller
Patricia White as Clara
William Edmunds as Antonio
Belle Mitchell as Giovanna
Ray Walker as Mr. Miller
Pedro de Cordoba as Horatio
The film was Warner Bros.' only foray into the horror genre in the 1940s and was Peter Lorre's last film with the studio.
Graham Baker was reported as working on a script for Warner Bros in 1945. Robert Florey was assigned to direct with Andrea King and Paul Henreid to star. The screenwriter Curt Siodmak had originally written the film for Henreid, who turned it down. Robert Alda was cast instead.
Filming started 27 November 1945. The piece much played throughout the film is Brahms' transcription for left hand of the chaconne from Johann Sebastian Bach's Violin Partita in D minor, performed by Warner Bros. pianist Victor Aller. The hand of pianist Victor Aller is shown playing the piano and throughout the movie.