**SPOILERS** Working his usual 16 hour shift at the hospital Dr. Laurence Jefferies, Anthony Perkins, spots a confused and discombobulated stranger played by Charles Bronson in the emergency ward and a light-bulb light up in his head.
Laurence's sexy wife Frances, Jill Ireland, had been cheating on him and is about to leave for Paris to see her secret lover French journalist Paul Damien, Henri Garcin. With this stranger suffering from amnesia Laurence can now get his revenge without ever getting his hands dirty and ending up behind bars.
The stranger wants to go home but doesn't quite know where home is and Laurence volunteers to drive him to the Bogston train station where he can get a train to London where the stranger strangely feels that he comes from.
Found on East Cliff Beach the stranger has a nasty scratch on his chest as if he was being fought off by somebody, most properly a woman. Later in the movie we get a flashback, from the stranger, that he was involved in a rape and murder of a young woman on the beach.
Laurence instead of taking the stranger to Bogston Station takes him back to his home and manically conditions his unbalanced and violent mind, with drugs that he slips into his orange juice, to murder his wife's Frances lover Paul but makes it as if Frances is really his, the stranger's, wife who cheating on him.
Laurence is so obsessed in getting the stranger to murder Paul that he overlooks the fact that he had a gun on him, that Laurence found in the stranger's raincoat,that should have tipped him off how dangerous and violent he really is.
Planting love letters from Paul, and a nude photo of Frances on the stranger's clothes whacks out the stranger's mind. This tricked him into thinking that Frances is his wife, and gets him all riled up and crazy and more then willing to do in her lover Paul.
Laurence also get's his brother in law Andrews, Adriano Magistretti, to get in touch, as a middle man, with Paul so he would come to England and talk his differences over with him in a clam and civilized way but in reality be confronted with the now mad and almost insane stranger. Laurence's plan works to perfection until the stranger and Paul meet at his front door, with him hiding like the coward that he is upstairs. It's then that something terribly goes wrong and the stranger balks. Instead of immediately shooting Paul Frances, who was unexpectedly with Paul outside in his car, Paul realizes that the stranger is not her husband at all but an impostor.
Undoubtedly this was Charles Bronson's best acting but the movie "Someone Behind the Door" is far from his best movie with a totally unbelievably story-line that doesn't give his acting any credit.
Anthony Perkins is so weird that I pity the patients that he's attending back at the hospital, or in his doctor's office, if you consider Charles Bronson, the stranger, as a prime example of his "top notch" medical work.
Jill Ireland is by far the most believable, with her lover Henri Garcin playing Paul a close second, of the actors in the movie with her shock and total confusion at the end of the movie when she meets her "husband" the stranger Charles Bronson, even though he's her husband in real life. The wild and furious fight that they have is inter-cut with the stranger's rape and murder of the young woman that caused his amnesia was by far the highlight of the movie.