The locked-room mystery is a subgenre of detective fiction in which a crime—almost always murder—is committed under circumstances under which it was seemingly impossible for the perpetrator to commit the crime and/or evade detection in the course of getting in and out of the crime scene.
Please add any suggestions to the comments and I'll get them on the list asap.
14.
by Sidney Paget, George Cavendish, Arthur Conan Doyle
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20.
by Edgar Allan Poe, Matthew Pearl
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25.
by Victor Sage, Joseph Sheridan Le Fanu
Note: Can also be used for:
Gothic square
Dark and Stormy Night square
Classic Horror square
Genre: Horror square
Genre: Mystery square
26.
by Various Authors, Martin Edwards
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29.
by Ross MacKenzie, Soji Shimada, Shika MacKenzie
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31.
by Yukito Ayatsuji, Ho-Ling Wong, Soji Shimada
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41.
by Maj Sjöwall, Per Wahlöö
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63.
by John Gielgud, Ralph Richardson, Arthur Conan Doyle
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Arguably, Dorothy L. Sayers's first two "Lord Peter and Harriet Vane" novels are locked room mysteries, too:
"Strong Poison" (ISBN 13: 9780061043505; ISBN 10: 0061043508) involves a meal jointly eaten down to the last crumb by two cousins, one of whom survives while the other ones dies;
and in "Have His Carcase" (ISBN 13: 9780061043529; ISBN 10: 0061043524) all the evidence points to the victim having died at a time when he can't possibly have died in reality.
Incidentally, for "Sign of Four" did you possibly add the book for the BBC adaptation starring Benedict Cumberbatch instead of Conan Doyle's actual novel? (Here's the Amazon page for the book you added: https://www.amazon.com/Sherlock-Sign-Four-BBC-Books/dp/1849904049)
A.C.D.'s original novel is (inter alia) here: ISBN 13: 9780140439076 (ISBN 10: 0140439072)
Ellery Queen: "The King Is Dead"
John Dickson Carr: " The Case of the Constant Suicides"
Edmund Crispin: "The Movin Toyshop"
Ruth Ware: "The Woman in Cabin 10"
Nevada Barr: "Firestorm", "Winter Study"
Maj Sjöwall, Per Wahlöö: "The Locked Room"
Edgar Wallace: "The Four Just Men"
David Pirie: "The Night Calls"
Robert van Gulik: "The Red Pavillion", "The Chinese Gold Murders"
Elizabeth George: "Payment in Blood"
P.D. James: "The Lighthouse", "Original Sin"
Dorothy L. Sayers: "Busman's Honeymoon"
Georgette Heyer: "No Wind of Blame", "Detection Unlimited"
Margery Allingham: "The Case of the Late Pig", "Death of a Ghost"
Ngaio Marsh: "A Man Lay Dead", "Final Curtain", "Tied Up in Tinsel", "Death and the Dancing Footman", "Hand in Glove", "Scales of Justice", "Overture to Death", "Night at the Vulcan"
Arthur Conan Doyle: "The Valley of Fear", "The Norwood Builder"
Agatha Christie: "They Do It With Mirrors", "The Seven Dials Mystery", "Dead Man's Mirror", "Death in the Clouds", "Murder at the Vicarage", "Sparkling Cyanide", "The Hollow", "Sad Cypress", "Three Act Tragedy", "Lord Edgware Dies", "Towards Zero", "Death on the Nile"