Veteran serial director George B. Seitz keeps things perpetually on the move in The Great Mail Robbery. Theodore von Eltz stars as Marine lieutenant Donald Macready, assigned by his commanding officer to squelch a train-robbery gang. Going undercover, Macready infiltrates the gang and monitors their every move.
| Actor | Role |
|---|---|
 Theodore von EltzLieutenant Donald Macready | Lieutenant Donald Macready |
 Frank NelsonSergeant Bill Smith | Sergeant Bill Smith |
 Jean FenwickLaura Phelps (as Jeanne Morgan) | Laura Phelps (as Jeanne Morgan) |
 Lee ShumwayPhilip Howard | Philip Howard |
 DeWitt JenningsCaptain Davis | Captain Davis |
 Cora WilliamsMrs. Davis | Mrs. Davis |
 Nelson McDowellSheriff | Sheriff |
 Charles Hill MailesStephen Phelps | Stephen Phelps |
 Yvonne HowellSally | Sally |