| Name | Character | Episodes |
|---|---|---|
| Charles Korvin | Inspector Paul Duval | 39 |
| George Pastell | Captain Pagano | 2 |
| Lisa Daniely | Helene | 2 |
| Donald Pleasence | Karl Haussman | 1 |
| Alan Gifford | Bonnier | 1 |
| Raymond Huntley | Schroeder | 1 |
| Peter Vaughan | Inspector | 1 |
| Barbara Shelley | Diana | 1 |
| John Le Mesurier | Monsieur Iamprou | 1 |
| John Crawford | Kustrinski | 1 |
| John Crawford | Keflik | 1 |
| John Crawford | Ben Stack | 1 |
| Mary Morris | Ingrid Hoffman | 1 |
| Michael Goodliffe | Wolf Barstrom | 1 |
| Mai Zetterling | Carol | 1 |
| Marne Maitland | Bhandari | 1 |
| Warren Mitchell | Willi | 1 |
| Lee Montague | Dikalos | 1 |
| Patrick Troughton | Sukru | 1 |
| Jean Anderson | Nun | 1 |
| Bernard Cribbins | Sid | 1 |
| Leslie French | Pimm | 1 |
| Cyril Shaps | Gamel | 1 |
| Cyril Shaps | Slade | 1 |
| Moira Redmond | Nina | 1 |
| Richard Gale | Ember | 1 |
| John Cairney | Lt. Gupta | 1 |
| Walter Gotell | Zeist | 1 |
| Walter Gotell | Fischer | 1 |
| William Franklyn | Nevil | 1 |
| George Pastell | Pagano | 1 |
| George Pastell | Capt. Pagano | 1 |
| Cec Linder | Captain Tully | 1 |
| Frederick Jaeger | Bernarde | 1 |
| Edward Jewesbury | Andrew Slater | 1 |
| Rona Anderson | Lena | 1 |
| Francis Matthews | Fawley | 1 |
| Walter Rilla | The Baron | 1 |
| John Horsley | Montell | 1 |
| John Longden | Lord Ruskington | 1 |
| Guy Deghy | Ritter | 1 |
| Stratford Johns | Inspector Chaublin | 1 |
| Robert Cawdron | Debre | 1 |
| Elizabeth Wilson | Michele | 1 |
| Esmond Knight | Von Schriber | 1 |
| Maurice Kaufmann | Ronald Millais | 1 |
| Harold Kasket | Lenoir | 1 |
| Harold Kasket | Thibault | 1 |
| Douglas Wilmer | Steinitz | 1 |
| Howard Lang | Commander Siddons | 1 |
| Anthony Dawson | Clouston | 1 |
| Alfred Burke | Martin Bekker | 1 |
| William Lucas | Cliff McGrath | 1 |
| Henry Oscar | Renoir | 1 |
| Ursula Howells | Miki | 1 |
| Ronald Leigh-Hunt | Hugo Ballard | 1 |
| Lloyd Lamble | Captain Merrick | 1 |
| Robert Brown | Sergeant at Car Impound | 1 |
| Robert Brown | Attendant | 1 |
| Peter Dyneley | LeRoy | 1 |
| Arnold Diamond | Inspector Krantz | 1 |
| Arnold Diamond | Lambert | 1 |
| Peter Illing | Captain Omar | 1 |
| Jan Holden | Jane Grant | 1 |
| Martin Wyldeck | German Police Chief | 1 |
| Richard Leech | Hanson | 1 |
| Richard Leech | Finn | 1 |
| Richard Leech | Garetta | 1 |
| Martin Benson | Ahmed | 1 |
| Phil Brown | Brownley | 1 |
| Francis de Wolff | Captain Gallard | 1 |
| Francis de Wolff | Captain Blink | 1 |
| Robert Rietti | Pinelli | 1 |
| Frederick Piper | Inspector Malcolm | 1 |
| Hazel Court | Carol LeDuc | 1 |
| David Kossoff | Professor Renee | 1 |
| Tommy Duggan | Cranby | 1 |
| Michael Brennan | Victor Perrot | 1 |
| André Maranne | Georges | 1 |
| Paul Stassino | Pavone | 1 |
| Annabel Maule | Amy | 1 |
| Basil Dignam | Insp. Hopkins | 1 |
| Harry Landis | Attendant | 1 |
| Michael Balfour | Russ | 1 |
| Michael Balfour | Inspector Hill | 1 |
| Philip Ray | Mr. Meyer | 1 |
| John Bentley | Dave Carson | 1 |
| Alan Tilvern | Johnny Stefano | 1 |
| Robert Arden | Marston | 1 |
| Meredith Edwards | Doctor Gorman | 1 |
| Glyn Owen | Gill | 1 |
| Patrick Jordan | Cpl. Khan | 1 |
| Brian Worth | Diplomat | 1 |
| David Davies | Colonel Briggs | 1 |
| Carl Duering | Dr. Berger | 1 |
| Carl Duering | Tony D'Ambrosio | 1 |
| Bruno Barnabe | Capt. Dekker | 1 |
| Frederick Leister | Sir Isaac Spendler | 1 |
| Christopher Rhodes | Howard | 1 |
| Victor Beaumont | Esler | 1 |
| Oscar Quitak | Abdul | 1 |
| Dervis Ward | Colonel | 1 |
| Christina Gregg | Maria | 1 |
| Laurence Payne | Porton | 1 |
| Errol John | Sergeant Hamid | 1 |
| Alec Mango | Gomiero | 1 |
| Austin Trevor | Dr. Martin | 1 |
| Susan Travers | Carol | 1 |
| Lionel Murton | Thakeray | 1 |
| Colette Wilde | Anna Grauber | 1 |
| Colette Wilde | Shana | 1 |
| Gerard Heinz | Mr. Dorner | 1 |
| David Knight | Harry | 1 |
| Bill Nagy | Bill Grant | 1 |
| Bill Nagy | Sash Moran | 1 |
| Donald Morley | Lebrun | 1 |
| Leonard Sachs | Muller | 1 |
| Leonard Sachs | Carlo | 1 |
| Trevor Reid | Inspector Holt | 1 |
| Trevor Reid | Cummings | 1 |
| Arthur Gomez | Costa | 1 |
| Gordon Tanner | Clyde | 1 |
| Ernest Clark | Inspector MacAndrew | 1 |
| Reed De Rouen | Simms | 1 |
| Donald Stewart | Steve Taylor | 1 |
| Jack Stewart | MacLelland | 1 |
| Keith Peacock | Hotel Guest | 1 |
| Kevin Stoney | Onno | 1 |
| John Salew | Moltz | 1 |
| Rupert Davies | Coetzee | 1 |
| Gaylord Cavallaro | David Baker | 1 |
| Marla Landi | Maria | 1 |
| Guy Rolfe | Mr. George | 1 |
| Leslie Weston | Doc Carson | 1 |
| Nanette Newman | Hannah | 1 |