Obsession, released in the United States as The Hidden Room, is a 1949 British crime film directed by Edward Dmytryk.

[3] Clive Riordan, a wealthy London psychiatrist, learns that his wife Storm is romantically involved with Bill Kronin, an American.

After kidnapping Kronin at gunpoint, Riordan keeps him prisoner for months in a hidden room accessed from a nearby garage while authorities mount a search for the missing American.

Riordan's plan appears to be succeeding until Superintendent Finsbury from Scotland Yard visits the doctor's office.

Feeling the noose tightening, Riordan decides it’s time to act and poisons Kronin, only to discover that he has trained Monty to empty the acid bath by pulling the plug chain.

[9] The film's director Edward Dmytryk, had recently left Hollywood following his appearance before the House Un-American Activities Committee.

[10] He travelled to England in mid-1948 and was granted a work permit by the Ministry of Labour under the foreign directors' quota agreement between producers and the film industry's trade unions.