In the noir cycle, if you were looking for sinister skulduggery, you needn't have searched any farther than the closest mental institution. Creepy snake-pits were the setting, in whole or in part, of (just to name a few) Strange Illusion, Spellbound, Shock, The High Wall and Shock Corridor. But maybe the scariest asylum of them all was La Siesta, in Oscar (later, Budd) Boetticher's Behind Locked Doors.
You'd have to be crazy to go there, because while its name promises cozy afternoon naps, what it delivers is apt to be the big sleep. Private eye Richard Carlson doesn't want to go either, but he up and falls for a reporter (Lucille Bremer) who persuades him to do the inside legwork on a story she was after. (A corrupt judge has vanished, and his girlfriend has been making nocturnal visits to La Siesta, where she's ushered in through a side door.) So they fool a doctor in giving Carlson a diagnosis of manic depression, and he becomes an inmate.
Inside, Carlson uncovers a web of secrets and lies, enforced by sadistic attendant Douglas Fowley with the help, as a last resort, of a punch-drunk prizefighter who's kept in a cage-like cell (Tor Johnson, who also graced Plan 9 From Outer Space). The intrigue centers around the judge, who's paying off the head of the hospital to hide him. But, when suspicions are raised by a deliberate act of arson, Carlson becomes the top item on the hit list....
At barely more than an hour, the movie doesn't have any time to waste, so Boetticher moves at a pretty fast clip (only the ending seems rushed). He lays on the shadows, too, with characters ominously silhouetted against walls and doors. More of an old dark house story, really, than a more freighted and ambiguous noir, Behind Locked Doors sets its sights modestly but achieves them handily.
Note: The plot summary of this movie in the `bible' Silver and Ward's Film Noir: An Encyclopedic Reference to the American Style is hopelessly garbled, as though two different films had become confused.