 | Jeffrey Lynn | ... | Kurt Franken |
| Philip Dorn | ... | Eric Franken |
| Kaaren Verne | ... | Sylvia Helmuth |
| Mona Maris | ... | Fräulein Gessner - Heller's secretary |
| Peter Whitney | ... | Alex Schumann, Underground Member |
| Martin Kosleck | ... | Col. Heller |
| Erwin Kalser | ... | Dr. Albert Franken |
| Ilka Grüning | ... | Frau Franken (as Ilka Gruning) |
| Frank Reicher | ... | Prof. Hugo Baumer |
| Egon Brecher | ... | Herr Director of the Chemical Institute |
| Ludwig Stössel | ... | Herr Gustav Müller, a Neighbor (as Ludwig Stossel) |
| Hans Schumm | ... | Heller's Aide |
| Wolfgang Zilzer | ... | Walter Hoffman |
| Roland Varno | ... | Ernst Demmler, Underground Member |
| Henry Brandon | ... | Josef Rolf, Underground Member Shot by Gestapo |
| Lotte Palfi Andor | ... | Greta Rolf, undergrounder (as Lotte Palfi) |
| Lisa Golm | ... | Ella aka Elsa, Franken's Housekeeper |
| Louis V. Arco | ... | Otto (as Louis Arco) |
| Roland Drew | ... | Gestapo Officer with Pencil Mustache |
| rest of cast listed alphabetically: |
| Louis Adlon | ... | Karl, Baggage Attendant (uncredited) |
| Lester Allen | ... | Herr Krantz (uncredited) |
| Rudolph Anders | ... | Official (uncredited) |
| Edit Angold | ... | Maxel's Cashier (uncredited) |
| Walter Bonn | ... | Lieutenant (uncredited) |
| Glen Cavender | ... | Man Giving Sylvia Baggage Claim Ticket (uncredited) |
| Hans Conried | ... | Herman, Underground Member (uncredited) |
| Gretl Dupont | ... | Sylvia's Landlady (uncredited) |
| Arno Frey | ... | Guard (uncredited) |
| Frederick Giermann | ... | Radioman (uncredited) |
| Eddie Graham | ... | Man in Phone Booth (uncredited) |
| Ludwig Hardt | ... | Tobacco Clerk (uncredited) |
| Ernst Hausman | ... | Rudi (uncredited) |
| David Hoffman | ... | Willi, Underground Member (uncredited) |
| Willy Kaufman | ... | Tobacco Customer (uncredited) |
| Rolf Lindau | ... | Radioman (uncredited) |
| Carl Ottmar | ... | Official (uncredited) |
| Paul Panzer | ... | Janitor (uncredited) |
| John Piffle | ... | Herr Maxel, Cafe Proprietor (uncredited) |
| Otto Reichow | ... | Gestapo Agent (uncredited) |
| Henry Rowland | ... | Paul, Underground Member on Motorcycle (uncredited) |
| Lionel Royce | ... | Concentration Camp Captain (uncredited) |
| Norbert Schiller | ... | Blind News Vendor (uncredited) |
| Robert R. Stephenson | ... | Gestapo Agent (uncredited) |
| Arthur Tovey | ... | Railroad Station Extra (uncredited) |
| Ernö Verebes | ... | Maxel's Headwaiter (uncredited) |
| Henry Victor | ... | Gestapo Agent (uncredited) |
| Frederick Vogeding | ... | Announcer Reporting Demise of Illegal Broadcasts (uncredited) |
| Wilhelm von Brincken | ... | Capt. Bornsdorff (uncredited) |
| Hans von Morhart | ... | Gestapo Agent (uncredited) |
| Crane Whitley | ... | Gestapo Agent (uncredited) |
| Hans Wollenberger | ... | News Vendor (uncredited) |
company.