- Aubrey Woods - Philippe Mortemartre
- Hugh Burden - Guillaume Serre
- Wilfrid Brambell - Jacob
- Peter Copley - Xavier Marton
- Margaretta Scott - Mme. Debul
- Erik Chitty - Hotel Clerk
- Pete Murray - Philippe
- John Robinson - Professor Gouin
- Nanette Newman - Odette
- Alan Tilvern - Van Damme
- Patrick Newell - Danielou
- Clive Morton - Gautier
- Ballard Berkeley - Dr. Pardon
- Paul Eddington - Harry Brown
- Pamela Brown - Giselle
- Dandy Nichols - Concierge
- Jean Anderson - Madame Gallet
- Alex Scott - De Greef
- Eric Thompson - Pierre Eyraud
- Griffith Jones - Dr. Bellamy
- Marius Goring - Peter the Lett
- Philip Stone - Father Demian
- Roger Delgado - Pepito
- Alex Gallier - Harris
- Peter Stephens - Baron Lagrange
- Colin Douglas - Yan
- Peter Barkworth - Sergeant
- Bernard Kay - Francois
- Peter Illing - Nikos Strophades
- William Franklyn - Count Maurice
- Charles Lloyd Pack - Tardivot
- Gordon Gostelow - Georget
- Toke Townley - Charlot
- Colin Jeavons - Jean Metayer
- Patsy Smart - Mademoiselle Rinquet
- Maurice Denham - Tiburce de St. Hilaire
- William Mervyn - Doctor
- Neil McCarthy - Henri Trochu
- Charles Farrell - Marcellin
- Robert S. Young - Court Usher (as Robert Young)
- Robert S. Young - Page
- Meredith Edwards - Foreman
- Patrick Boxill - Baptiste
- John Bown - Emile Gautier
- Terry Raven - Jean Pierre
- Beckett Bould - Albert
- John Hart - Character in Corridor (uncredited)
- Noel Hood - Mme. Serre
- Andrée Melly - Ernestine
- Jean Marlow - The Waitress
- Jack Rodney - Sad Freddie
- John Barrett - Barman
- Charmian Eyre - Jenny Sorel
- Freda Jackson - Rose Alfonsi
- Thomas Gallagher - Fred Alfonsi
- Joan Young - Rosalie Moncoeur
- Ernst Ulman - Dr. Bloch
- April Olrich - Arlette
- Michael Hitchman - Police Doctor
- Maria Antippas - Betty
- Linda Castle - Tania
- Stan Simmonds - Oscar
- Leonard Grahame - Gendarme
- Harold Scott - Dr. Pardon
- David Webb - Alain Lagrange
- Campbell Singer - Inspector Pyke
- Susan Burnet - Georgette
- Cecil Brock - Receptionist
- Robert Hunter - Gaston Grimal
- John Scott Martin - Cloakroom Attendant
- Marie Ney - Madame Besson
- Jane Barrett - Yvette Sudre
- Noel Howlett - Comeliau
- Anthony Newlands - Theo Besson
- Kevin Brennan - Charles Besson
- Stanley Van Beers - Inspector Castaing
- John Barrard - Antoine
- Nan Marriott-Watson - Madame Trochu
- Arthur Goullet - Dr. Jolly
- Veronica Wells - Rose Trochu
- Michael Logan - Hotel Manager
- Keith Marsh - Waiter
- Kathleen Saintsbury - Marie
- Kathleen Saintsbury - Sister
- Kenneth Adams - Booking Clerk
- Renée Houston - Ja-Ja
- Diana Beaumont - Gina
- Blanche Fothergill - Madame Martine
- David Lander - Giovani
- Annette Carell - Sylvie
- John Gatrell - Boutigues
- Martin Sterndale - Police Officer
- David Grahame - Albert
- John Kidd - Male Secretary
- Richard Warner - Louis Potin
- William Sherwood - Doctor
- Gareth Davies - Henri Gallet
- Anne Ridler - Eleanor
- Molly Veness - Post Office Clerk
- Anne Blake - Madame Canut
- Denis Cowles - Emile Gallet
- Shirley Patterson - Maid
- Marian Spencer - Mrs. Wilcox
- Leslie French - Emile
- Arnold Marlé - Duval
- Frederick Treves - Lechat
- Edna Petrie - Postmistress
- Zoreen Ismail - Anna
- Charles Hill - Paul
- Dani Seper - Bette
- Peggy Thorpe-Bates - Germaine Gouin
- Annabel Maule - Dr. Lucile Decaux
- Valerie White - Antoinette Ollevie
- John Salew - Dr. Paul
- Totti Truman Taylor - Madame Cornet
- George Betton - Louis
- Dennis Edwards - Dr. Lanvin
- Eugene Leahy - Old Man In Library
- Perlita Neilson - Sister Marie des Anges
- Gladys Boot - Madame Bellamy
- Barbara Cavan - Mother Superior
- Freda Bamford - Sister Aldegonde
- Mary Kenton - Popine
- Peter Elliott - Inspector Mansuy
- Nicolette Bernard - Olga
- John Ruddock - Duffleux
- Janet Barrow - Babette
- Michael Alexander - Sergeant
- Mervyn Johns - Inspector Fumel
- John Tate - Jericho
- Gerald Cross - Belloir
- Richard Burrell - Lombard
- Allan McClelland - Armand
- Denis Holmes - Inspector Bergsma
- Arthur Lawrence - Doctor
- Norman Mitchell - Café Proprietor
- George Little - Jean
- Joyce Barbour - Concierge
- Michael Golden - Councillor Duché
- Michael Golden - Landlord
- Olga Lindo - Madame Cremieux
- Rita Davies - Germaine
- Rodney Burke - Extra (uncredited)
- Harold Kasket - Marchand
- Wolfe Morris - Carl
- Georges Simenon
- Andrew Osborn
- Bill Luckwell
- Ron Grainer
Neil McCarthy interpreta a Henri Trochu en la serie.
Aubrey Woods hace el papel de Philippe Mortemartre.
Philip Stone interpreta a Father Demian en la serie.
Rupert Davies interpreta a Chief Inspector Maigret en la serie.
Ewen Solon hace el papel de Lucas.
Henry Oscar interpreta a Inspector Lognon en la serie.
Helen Shingler hace el papel de Madame Maigret.
Neville Jason hace el papel de Lapointe.
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