 | 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) |
Watching Underground makes me wish that TCM would do an anthology of great B-movies. Limited budgets imposed constraints on production values -- sound stages and back lots instead of locations, black & white instead of color, character actors in leading roles. What budgets didn't constrain was acting, directing and writing. And what's cool is that there were lots of them, especially from the studio system, where great talent was on staff.
I don't think I've seen a wartime propaganda flick that pulls out all the stops quite like this one. Vile Nazis in their spiffy Nazi uniforms, sadism, torture, whips, dungeons, betrayal, sabotage, righteous rants by old professors...all here! Tight production and right casting make this a delicious grand guignol. Despite the grim theme, there are some pretty funny Hogan's Heroes moments. Example: a thuggish Gestapo underling is bragging to his secretary about a ghastly new torture method he's invented and complaining about Himmler's taking the credit. The secretary, who's in the underground, replies, barely containing her sarcasm, "Don't worry, I'm sure you'll get a promotion."
And then, there's the ending, when one must face an excruciating dilemma -- to do something horrible and cruel for the greater good. It's something I don't know if I'd have the courage to do. Would you?