 | Allan Lane | ... | Sergeant Dave King |
 | Robert Strange | ... | John Kettler |
 | Robert Kellard | ... | Corporal Tom Merritt, Jr. |
 | Lita Conway | ... | Linda Merritt |
 | Herbert Rawlinson | ... | Inspector King [chs 1-4] |
 | Harry Cording | ... | Wade Garson |
 | Bryant Washburn | ... | Matt Crandall |
 | Budd Buster | ... | Vinegar Smith |
 | Stanley Andrews | ... | Tom Merritt Sr. [Ch. 1] |
 | John Davidson | ... | Dr. Shelton [Chs 4, 5] |
 | John Dilson | ... | Doctor (inventor) [Ch. 1] |
 | Paul McVey | ... | His Excellency [Ch. 1] |
 | Lucien Prival | ... | Admiral [Ch. 1] |
 | Norman Willis | ... | Submarine Captain [Chs. 1,12] |
 | Tony Paton | ... | Henchman LeCouteau |
| rest of cast listed alphabetically: |
 | John Bagni | ... | Higgins, Cabin Henchman [Ch. 7] (uncredited) |
 | Earle D. Bunn | ... | Smelter Truck Driver [Chs. 8-9] (uncredited) |
 | Tommy Coats | ... | Henchman (uncredited) |
 | George DeNormand | ... | Fake Inspector Kent [Ch. 11] (uncredited) |
 | Curley Dresden | ... | Kelly (miner) [Chs. 1, 3] (uncredited) |
 | Douglas Evans | ... | Sergeant (wireless operator) [Chs. 1, 11] (uncredited) |
 | James Fawcett | ... | Smelter heavy #2 [Chs. 8-9] (uncredited) |
 | George Ford | ... | Paralytic #3 [Ch. 4] (uncredited) |
 | Bud Geary | ... | Klondike (uncredited) |
 | Duke Green | ... | (uncredited) |
 | Sam Harris | ... | Sir Harold Bolton [Ch. 11] (uncredited) |
 | Bob Jamison | ... | Pete (uncredited) |
 | Bruce Kellogg | ... | Const. MacCloud (uncredited) |
 | Walter Lowe | ... | Paralytic #2 [Ch. 4] (uncredited) |
 | Ted Mapes | ... | Blake (gang pilot) [Chs. 2-4, 7, 9] (uncredited) |
 | Dave Marks | ... | Knife heavy [Ch. 6] (uncredited) |
 | George Plues | ... | Train brakeman [Ch. 5] (uncredited) |
 | Wallace Reid Jr. | ... | Constable Doyle [chs 2, 9, 12] (uncredited) |
 | Loren Riebe | ... | Fake Inspector Dinwoodie [Ch. 11] (uncredited) |
 | Dick Simmons | ... | Const. Carter (uncredited) |
 | Cy Slocum | ... | Sanitarium heavy [Ch. 4] (uncredited) |
 | William Stahl | ... | Corporal Bob Hastings [Ch. 1] (uncredited) |
 | Denny Sullivan | ... | Paralytic #1 [Ch. 4] (uncredited) |
 | Al Taylor | ... | Henchman Red [Chs. 5-8, 10, 12] (uncredited) |
 | Duke Taylor | ... | Smelter heavy #1 [Chs. 8-9] (uncredited) |
 | Ken Terrell | ... | Henchman Al [Chs. 1, 3-5] (uncredited) |
 | Charles Thomas | ... | Henchman Bayliss [Ch. 12] (uncredited) |
 | Al Thompson | ... | Paralytic #4 [Ch.4] (uncredited) |
 | Richard Travis | ... | Const. Hallett (uncredited) |
 | Dale Van Sickel | ... | Gang radioman [Ch. 2] (uncredited) |
 | Frank Wayne | ... | Brant, Speedboat driver-thug [Chs. 1, 4. 9] (uncredited) |
 | Robert Wayne | ... | Lieutenant [Ch. 1] (uncredited) |
 | Bill Wilkus | ... | Bill (sanitarium heavy) [Ch. 4] (uncredited) |