Obsession

Clive Riordan, a wealthy London psychiatrist, learns that his wife Storm is involved with Bill Kronin. He decides to exact revenge by staging the perfect murder. This revelation becomes the catalyst for a meticulously planned crime that will unfold over months.

Riordan resolves to abduct Kronin and keep him alive to avoid any obvious link to himself. He envisions a 'perfect' crime that would remove his rival without leaving a trace of motive or opportunity. The plan is to remove Kronin from the scene while his wife remains unaware of the danger.

Kronin is kidnapped at gunpoint and imprisoned in a hidden room accessed from a garage in a bomb-damaged area of London. Riordan controls every movement of the prisoner and begins the long, quiet captivity. The grim setup marks the start of the prolonged plot.

Kronin remains imprisoned for months, during which Riordan fine-tunes his alibi and searches for a safe disposal. Authorities mount a search for the missing American, but leads dry up after a few weeks. Riordan believes the longer the captive remains, the less likely detection will be linked to him.

Riordan makes daily visits to Kronin with food and supplies. Monty, Riordan's dog, trails him noisily, risking discovery as the secret room stays hidden. Kronin takes note of the dog and of the constant surveillance that surrounds his imprisonment.

Riordan begins assembling the means to dispose of Kronin by dissolving him in acid. He brings hot water bottles filled with acid to the hidden bath, fearing Monty might reveal the location if the plan were exposed. The 'perfect' method now seems within reach.

Riordan moves to lethal action and poisons Kronin, hoping the plot will succeed. He discovers, however, that Monty has been trained to pull the plug chain and drain the bath, foiling the murder just as it seems to be working.

Superintendent Finsbury from Scotland Yard visits Riordan's office, ostensibly to check on the missing dog. Their talks reveal that Finsbury suspects Riordan and connects him to the ongoing American case through subtle clues.

Riordan overhears a conversation between Storm and Finsbury, confirming that the police are closing in. Realizing danger, he resolves to act and intensifies his plan against Kronin.

Police find Riordan’s car in the garage, leading them to the hidden room and Kronin’s still-living body. Realizing his plan has failed, Riordan resigns himself to fate and awaits arrest at his club.

Finsbury returns and reveals that Kronin has survived, meaning Riordan has escaped a murder charge for now. The immediate danger passes, though Riordan remains under scrutiny and the affair lingers as a potential liability.

Storm visits Kronin as he convalesces in hospital and tells him she will travel abroad for a while. Monty, loyal to Kronin, jumps his lead and pads over to the hospital bed, underscoring a fragile, quiet bond as Storm leaves them together.