 | Victor Jory | ... | Spike Holland |
 | Iris Meredith | ... | Valerie Howett |
 | James Craven | ... | Abel Bellamy |
 | Robert Fiske | ... | Savini |
 | Dorothy Fay | ... | Elaine Bellamy |
 | Forrest Taylor | ... | Parker Howett |
 | Jack Ingram | ... | Henchman Brad |
 | Joseph W. Girard | ... | Inspector Ross |
 | Fred Kelsey | ... | Capt. Thompson |
 | Kit Guard | ... | Dinky Stone, Henchman-Radio Man |
| rest of cast listed alphabetically: |
 | George Lloyd | ... | Henchman (scenes deleted) |
 | Jack Cheatham | ... | Policeman [Ch. 1] / Detective Charlie [Ch. 7] (uncredited) |
 | Edmund Cobb | ... | Stevens, Agent 4-X, thug pilot [Chs. 9-10] (uncredited) |
 | Kernan Cripps | ... | Frank, Train Ticket Taker [Ch. 1] (uncredited) |
 | Charles Dorety | ... | Thug [Ch.13] (uncredited) |
 | Kenne Duncan | ... | Michael Bellamy (uncredited) |
 | Herbert Evans | ... | Henderson, the butler (uncredited) |
 | Franklyn Farnum | ... | Pete, lab guard [Chs. 11, 13-14] (uncredited) |
 | Al Ferguson | ... | Henchman Butch (uncredited) |
 | Eddie Fetherston | ... | Henchman Turk Martin [Chs. 2-3] (uncredited) |
 | Chuck Hamilton | ... | Henchman Kardak (uncredited) |
 | Harry Harvey | ... | Martin, thug posing as Blinky [Ch. 2] (uncredited) |
 | Edward Hearn | ... | Policeman [Ch. 15] (uncredited) |
 | Lloyd Ingraham | ... | Worthington, the attorney [Ch. 1] (uncredited) |
 | Warren Jackson | ... | Charlie, the Theater Attendant [Ch. 1] (uncredited) |
 | J. Paul Jones | ... | Henchman Tinder [Chs. 1-6] (uncredited) |
 | Johnny Kascier | ... | Henchman Jake [Chs. 1-8] (uncredited) |
 | Charles King | ... | Henchman Tardoni [Chs. 1-6] (uncredited) |
 | Tom London | ... | Detective with Shiner [Ch. 7] (uncredited) |
 | Sam Lufkin | ... | Thug [Ch. 4] (uncredited) |
 | Mary MacLaren | ... | Mrs. Patton (uncredited) |
 | Knox Manning | ... | Narrator (voice) (uncredited) |
 | Bruce Mitchell | ... | Policeman [Ch. 15] (uncredited) |
 | Bud Osborne | ... | Lanton, garage henchman [Chs. 3, 5] (uncredited) |
 | Constantine Romanoff | ... | Henchman West (uncredited) |
 | Dick Rush | ... | Policeman [Ch. 1] (uncredited) |
 | Cy Schindell | ... | Henchman Darcy [Chs. 2-3] (uncredited) |
 | Harry Tenbrook | ... | Henchman Vrooner [Chs. 1-8] (uncredited) |

| Anthony Warde | ... | Henchman Lefty Brent [Ch. 1] (uncredited) |
 | Duke York | ... | Martel aka Harry Madison (uncredited) |
 | Bert Young | ... | Henchman Biff [Chs. 5-15] (uncredited) |
This is a pretty unusual serial. It took me two tries to get into it, but then I was hooked. The plot is no more than perfunctory and seems like it was stitched together out of random clichés as the writers went along, but a few episodes in things take a truly delightful turn into the bizarre. It feels as if the writer, director, and/or cast began to feel bored by the tripe they were enacting and decided to have some fun with it. The supposedly diabolical mastermind suddenly seems like the headmaster at a school for painfully inept crooks, constantly bemused but tolerant of his incompetent charges, and the cliffhangers and action sequences begin to feel like big jokes. My favorite shot: the hero is trapped in one of those rooms that slowly fill with water and the villain, after setting the trap in motion, turns to his cohort with a shrug and a wry grin that seems to say "The old flooded room trick again --- well, what're ya gonna do?" Unfortunately the serial runs out of steam towards the end and falls back on the usual tired hi-jinks, but for a while it's a delight.