Dr. Laurence Jeffries (Anthony Perkins) is a neurosurgeon, obsessed with his work and married to Frances Jeffries (Jill Ireland). When Frances objects to her husband’s lack of dedication to her, prioritizing his work instead, the neurosurgeon does nothing to change the status quo. Soon his wife finds a lover, thereby leaving the doctor enraged. As a means of exacting revenge on his cheating spouse, the brilliant and somewhat mad neurosurgeon concocts a plan that includes one of his patients. In comes The Stranger (Charles Bronson), a patient suffering from amnesia, who is convinced by Jeffries that Frances is his wife, with the doctor counting on the amnesiac killing her in a rage fit. Jeffries thinks his plan is foolproof because the man is not supposed to remember committing the murder, but things escalate soon enough. Someone Behind the Door truly was an international production.

French novelist and screenwriter Jacques Robert wrote a short story which was the basis for the script, then he worked on the screenplay with Marc Behm, American screenwriter/novelist and lover of all things French. In the end, Hungarian-born French director Nicolas Gessner came in to both help them finish the script and helm the film itself. Someone Behind the Door was shot in Folkestone, England, with the three main characters being Americans. The beautiful locations offer a perfect backdrop for this diabolical scenario to play out behind fancy closed doors, with lives that seem perfect from the outside. Many praised Bronson's performance, seeing as how this role involved less action than was the case with his previous films, thereby enabling him to show his acting chops.