Ken Williams is determined to discover the identity of the mysterious Rattler, who preys upon railroads and transportation companies like that owned by Jane Corwin. The Rattler is especially difficult to catch because of his skill at disguising himself as other people.
| Actor | Role |
|---|---|
 Ken MaynardKen Williams | Ken Williams |
 Verna HillieJane Corwin | Jane Corwin |
 Hooper AtchleyDr. Edwards | Dr. Edwards |
 Edward HearnLake | Lake |
 Syd SaylorBreezy Baker | Breezy Baker |
 Edward EarleFrank Blayden | Frank Blayden |
 Al BridgeTom Henderson | Tom Henderson |
 Bob KortmanRattler Henchman Hank | Rattler Henchman Hank |
 Lew MeehanRattler Henchman Red | Rattler Henchman Red |
 George ChesebroRattler Henchman Anderson | Rattler Henchman Anderson |
 Tom LondonRattler Henchman Morgan | Rattler Henchman Morgan |
 Lynton BrentMathews, Telegrapher | Mathews, Telegrapher |
 Gene AutryTeamster Thomas (ch's 6-8) (uncredited) | Teamster Thomas (ch's 6-8) (uncredited) |
 Smiley BurnetteLake Teamster (ch's 6-7) (uncredited) | Lake Teamster (ch's 6-7) (uncredited) |
 TarzanTarzan | Tarzan |