- Diana Quick - Cecilia Weiss
- James Lance - Barrett Underhill
- Simone Kirby - Sister Grace
- Mary Healey - Mrs. Blake
- Andrew Bicknell - Exorcist
- James Fleet - Dr. Pilsen
- Andrea Lowe - Beatrice Upton
- Jeremy Swift - Dr. Henry Whitaker
- Owen Teale - Professor Havensling
- Emily Hampshire - Madame Korzha
- Nathan Stewart-Jarrett - Elias Downey
- Enuka Okuma - Jane Downey
- Angela Curran - Vera Stuffts
- Esh Alladi - Dr. Kasad
- Adam Nagaitis - Sergeant George Gudgett
- Tom Canton - Paul Hargreaves
- Jobie McPartland - Terrified Woman (uncredited)
- Sarah Abbott - Libby Cotter
- Lara Jean Chorostecki - Clara Reid
- Billy MacLellan - Constable Billy McKinnon
- Peter Outerbridge - Thomas Edison
- Emily Carey - Mary Conan Doyle
- Noah Jupe - Kingsley Conan Doyle
- Tim McInnerny - Chief Inspector Horace Merring
- Jacob Blair - Benjamin Graves
- Bo Martynowska - Young Woman (as Bo Martyn)
- Paddy C Courtney - Mr. Gaines
- Louise Delamere - Touie Doyle
- Edward Akrout - Henry
- Patrick Carney Junior - Upper Class Gent
- Lady Conny Sharples - Amanda Posh (as Conny Sharp)
- Adelayo Adedayo - Winnie
- Penny Downie - Mrs. Sulzbach
- Philip Gascoyne - Scotland Yard Detective
- Amanda Lawrence - Sister Mathilda
- Eileen O'Brien - Sister Fabian
- Tereza Srbova - Natalia
- Tereza Srbova - Natalie
- Gavin Williams - Patron #3
- Sian Breckin - Margery McGuire
- Laura Fraser - Lydia Belworth
- Samuel Joslin - Peter Bennett
- Ruth Lass - Clara Bennett
- Phil Nice - Reverend Gilby
- Andrew Bridgmont - Dr. Perlow
- Nicholas Burns - Frederick Batch
- Neil Broome - The Coughing Man
- Marshall Griffin - Security Guard
- Amy Huberman - Mrs. Anne Batch
- Nig Richards - Mourner
- John Smeathers - Blind Man (uncredited)
- Blake Harrison - Lyman Biggs
- Sebastian Croft - Newsie
- Helen Millar - Isobel Underhill
- Tommy McDonnell - Nigel Pennington
- Natasha Jean Sparkes - Sophie (as Natasha Sparkes)
- Dritan Kastrati - Vladimir Palinov
- Dean Forster - Herbert Oglivie
- Graham Burton - Clown
- Alina Chan - Escort
- Yahya Baggash - Police Witness (uncredited)
- Jason Redshaw - Brothel Customer (uncredited)
- Lily-Rose Aslandogdu - Julia Hargreaves
- Emilia Forster - Helena Wood
- Lex Shrapnel - Mitchell Pearce
- Dennis O'Donnell - Dinner Guest (uncredited)
- Janine Duvitski - Martha
- Thomas Howes - Constable Booth
- Joel Morris - Jim Gorton
- Reece Noi - Daniel Berry
- Paul Warren - First Alien
- Sandy Kate Slade - Cavedweller (uncredited)
- Ewen Bremner - Sherlock Holmes
- Risteard Cooper - Charles Doyle
- Martin Gledhill - Lunatic
- Stacey Gough - Head Guard
- Charlotte Hope - Molly Morgan
- Lewis McGowan - Young Doyle
- Chu Omambala - Dr. Randall
- Joplin Sibtain - Dr. Chandra (as Chook Sibtain)
- Joe Sims - Nathaniel
- Andrew Regan - Estate Agent (uncredited)
- Tom Bishop Jr. - Carriage Driver
- Andy Gillies - Pumley
- Anna Koval - Liliana
- Kevin Mains - Lachlan MacBride
- Paul Ritter - Bram Stoker
- Elias Toufexis - Roland Carson
- Natalie Krill - Amelia
- Simon Northwood - Mr. Emmett Reid
- Ali Momen - Rustom Avari
- Timothy Mooney - Mr. Turner (as Tim Mooney)
- Daniel Matmor - Rabbi
- Justin Rutledge - Theodore Weiss
- Kjartan Hewitt - Reverend Harley
- Brandon Oakes - Walt
- Nicolas Van Burek - Stuart Branowski
- Mark Caven - Sherlock Holmes
- Dave Reachill - Hotel Patron (uncredited)
- Richard Price - Houdini Stage Hand (uncredited)
- Nazrin Choudhury
Ewen Bremner interpreta a Sherlock Holmes en la serie.
Emily Hampshire interpreta a Madame Korzha en la serie.
Jeremy Swift interpreta a Dr. Henry Whitaker en la serie.
Michael Weston interpreta a Harry Houdini en la serie.
Stephen Mangan hace el papel de Arthur Conan Doyle.
Rebecca Liddiard interpreta a Constable Adelaide Stratton en la serie.
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