A wealthy lord dies and is entombed with a valuable deposit of jewels. Seven keys are required to unlock the tomb and get hold of the treasure. A series of mysterious events causes the keys to be scattered, and when trying to unravel the circumstances, the heiress of the fortune and her companion investigators become entangled in a web of fraud, deceit, torture, and murder.

DICK MARTIN'S last official job (as he believed) was to pull in Lew Pheeney, who was wanted in connection with the Helborough bank robbery. He found Lew in a little Soho cafe, just as he was finishing his coffee. "What's the idea, colonel?" asked Lew, almost genially, as he got his hat.

Dick Martin is leaving Scotland Yard. His final job, investigating a stolen book, takes him via a conversation with the librarian Sybil Lansdown to Gallows Cottage and a meeting with Doctor Stalletti. Tommy Crawler, Bertram Cody's chauffeur is also there. Arriving home, Martin finds Lew Pheeney being followed by a man for whom he recently worked.

Dick Martin is leaving Scotland Yard. His final job, investigating a stolen book, takes him via a conversation with the librarian Sybil Lansdown to Gallows Cottage and a meeting with Doctor Stalletti. Tommy Crawler, Bertram Cody's chauffeur, is also there. Arriving home, Martin finds Lew Pheeney being followed by a man for whom he recently worked. "Doing what?" demands Martin. Lew finally confesses. "I was trying to open a dead man's tomb!" The telephone rings. It is Mr. Havelock.

The Door with Seven Locks is a 1940 black-and-white British film, created and released shortly after the British Board of Film Censors lifted its mid-1930s ban on supernatural-themed and horror genre films. It was based on the novel The Door with Seven Locks by Edgar Wallace.

He waited suggestively, but Lew Pheeney shook his head. "I'm not telling. The story would give away a man who's not a good fellow, and not one I admire; but I can't let my personal feelings get the better of me, and you'll have to go on guessing. And I'm not lying, I'll tell you how it happened." He gulped down a cup of hot coffee and pushed cup and saucer away from him. "I don't know this fellow who asked me to do the work - not personally. He's been in trouble for something or other, but that's no business of mine. One night he met me, introduced himself, and I went to his house - brr!" he shivered. "Martin, a crook is a pretty clean man - at least, all the crooks I know; and thieving's just a game with two players; me and the police. If they snooker me, good luck to 'em! If I can beat them, good luck to me! But there's some dirt that makes me sick, just makes my stomach turn over. When he told me the job he wanted me for, I thought he was joking, and my first idea was to turn it in right away. But I'm just the most curious creature that ever lived, and it was a new experience, so, after a lot of think, I said 'Yes'. Mind you, there was nothing dishonest in it. All he wanted to do was to take a peep at something. What was behind it I don't know. I don't want to talk about it, but the locks beat me."