A variety of people are searching for a long-hidden treasure somewhere on an island. Chapters: 1. The Isle of Fear, 2. The Ghost Talks, 3. The Phantom Duel, 4. Buried Alive, 5. The Girl Who Vanished, 6. Trapped by the Flood, 7. The Cannon Roars, 8. The Circle of Death, 9. The Pirate's Revenge, 10. The Crash, 11. Dynamite, 12. The Bridge of Doom, 13. The Mad Flight, 14. The Jaws of Destruction, 15. Justice
| Actor | Role |
|---|---|
 Don TerryLarry Kent | Larry Kent |
 Gwen GazeToni Morrell | Toni Morrell |
 Walter MillerCarter 'The Shark' Collins | Carter 'The Shark' Collins |
| GGeorge RosenerCapt. Samuel Cuttle | Capt. Samuel Cuttle |
 Grant WithersRoderick Gridley | Roderick Gridley |
 Hobart BosworthDr. X | Dr. X |
| SSandra KarinaNurse Zanya | Nurse Zanya |
| PP.J. KellyProf. Gault | Prof. Gault |
 Yakima CanuttDreer (Mole-Men Leader) | Dreer (Mole-Men Leader) |
 William FarnumGeorge Brennan Westmore (Editor) | George Brennan Westmore (Editor) |
 Joe CaitsSaltwater Jerry [Chs.1,4-7,13-15] | Saltwater Jerry [Chs.1,4-7,13-15] |
 Colin CampbellHawkins (the Butler) [Chs. 1-3] | Hawkins (the Butler) [Chs. 1-3] |
 Dave O'BrienDet. Jameson [Chs. 4-7] | Det. Jameson [Chs. 4-7] |
 William RoylePaul Thorndyke [Ch.1] | Paul Thorndyke [Ch.1] |
 Warner RichmondCapt. Tom Stanton, alias Capt. Tom Faxton [Ch.1] | Capt. Tom Stanton, alias Capt. Tom Faxton [Ch.1] |