A British Mystery-Anthology series that aired on ITV from 1971 to 1973. The series showcased various detectives, and other protagonists created by literary contemporaries of Arthur Conan Doyle, creator of the titular sleuth, with each episode being adapted directly from a short story by said authors. The protagonists range from great detectives to gentleman burglars. Some of the better known characters include Dr. John Thorndyke, Max Carrados, Thomas Carnacki, Martin Hewit and Professor Augustus Van Dusen.
The series is also notable for featuring a vast ensemble cast of top UK actors; some already established, others still unknown at the time.
Actors featured in the series include: John Neville, Paul Darrow, Peter Vaughan, Roy Dotrice, Donald Pleasence, Michele Dotrice, Geoffrey Whitehead, Paul Eddington, Jeremy Irons, Caroline John, Roger Delgado, Jacqueline Pearce, James Bolam, Una Stubbs, Peter Bowles, John Levene, Donald Sinden, Frank Williams, Richard Hurndall, Windsor Davies, Judy Geeson, Richard Beckinsale, Michael Sheard, Christopher Timothy, Martin Jarvis, Douglas Wilmer, Michael Gough, Clifford Rose, Donald Pickering, Nicholas Courtney, Bernard Hepton, Neil McCarthy, Christopher Neame, Charles Gray, John Thaw, Catherine Schell, Philip Madoc, Laurence Payne, Mark Eden, Nicola Pagett, Carolyn Jones, Michael Aldridge, Barrie Ingham, Peter Sallis, Julian Glover, Derek Jacobi, Robin Ellis, Jean Marsh and Joss Ackland.
- Dr. John Thorndyke: forensic sleuth, created by R. Austin Freeman. (Played by John Neville and Barrie Ingham in A Message from the Deep Sea and The Moabite Cypher, respectively)
- Max Carrados: a blind private detective, created by Ernest Bramah. (Played by Robert Stephens in The Missing Witness Sensation)
- Horace Dorrington: a crooked private eye, created by Arthur Morrison. (Played by Peter Vaughan in The Affair of the Avalanche Bicycle & Tyre Co. Ltd, and The Case of the Mirror of Portugal)
- Simon Carne, alias Klimo: a gentleman burglar posing as a private detective; created by Guy Boothby. (Played by Roy Dotrice in The Duchess of Wiltshires Diamonds)
- Thomas Carnacki: an occult detective, created by William Hope Hodgson. (Played by Donald Pleasence in The Horse of the Invisible)
- Dixon Druce: private investigator, created by L.T. Meade and Robert Eustace. (Played by John Fraser in Madame Sara)
- Martin Hewitt: private detective, created by Arthur Morrison. (Played by Peter Barkworth in The Affair of the Tortoise and The Case of Laker, Absconded)note
- Lady Molly of Scotland Yard: police officer, created by Baroness Orczy. (Played by Elvi Hale in The Woman in the Big Hat)
- Romney Pringle: con artist turned private detective, created by Clifford Ashdownnote . (Played by Donald Sinden in The Assyrian Rejuvenator)
- Bernard Sutton: professional jeweller, created by Max Pemberton. (Played by Robert Lang in The Ripening Rubies)
- Polly Burton: a journalist, created by Baroness Orczy. (Played by Judy Geeson in The Mysterious Death on the Underground Railway)note
- Inspector Leo Lipinzki: South African policeman, created by George Griffith. (Played by Barry Keegan in Five Hundred Carats)
- Professor Van Dusen: The Thinking Machine, created by Jacques Futrelle. (Played by Douglas Wilmer in Cell 13 and The Superfluous Finger)
- John Laxworthy: gentleman thief, created by E. Phillips Oppenheim. (Played by Bernard Hepton in The Secret of the Magnifique)
- Eugene Valmont: French sleuth, created by Robert Barr. (Played by Charles Gray in The Absent-Minded Coterie)
- Lieutenant Holst: Danish policeman, created by Palle Rosenkrantz. (Played by John Thaw in The Sensible Action of Lieutenant Holst)
- Dagobert Trostler: Austrian detective, created by Balduin Groller. (Played by Ronald Lewis in Anonymous Letters)
- Duckworth Drew: Secret Service agent, created by William Le Queux. (Played by Derek Jacobi in The Secret of the Fox Hunter)
- Mr. Horrocks: naval officer, created by C. J. Cutcliffe Hyne. (Played by Ronald Fraser in The Looting of the Specie Room)
- Hagar Stanley: Gypsy, created by Fergus Hume. (Played by Sara Kestelman in The Mystery of the Amber Beads)
- Charles Dallas: barrister, created by John Oxenham. (Played by Robin Ellis in The Missing Q.C.s)
- Adaptational Jerkass: Thorndyke is presented here as arrogant and gruff. In the stories, he's more amiable and humble.
- Adaptational Nationality: The Van Dusen stories were originally set in America, here they're set in Britain.
- Amateur Sleuth: Bernard Sutton, Polly Burton, Professor Van Dusen, Mr. Horrocks and Hagar Stanley.
- Blind Justice: Max Carrados.
- Corrupt Cop: More like corrupt private detective. We have two in the forms of Horace Dorrington and Romney Pringle.
- Forensic Drama: The Thorndyke episodes.
- Occult Detective: Thomas Carnacki.
- Period Piece: The series is set in the late Victorian, and early Edwardian eras.
- Private Investigator: About half of the detectives are this.
- Romani: Hagar Stanley.