As rustled cattle have mysteriously disappeared, Johnny sends for his friend Hoppy, Hoppy arrives and immediately suspects Dan Slack. Realizing his telegram about Slack was intercepted, he locks up the operator Lafe knowing he can escape. Tailing Lafe he finds a secret entrance to a mine and inside finds the missing cattle. But Slack's men also find him just as the cattle are stampeded through the mine shaft.
William Boyd
as Hopalong Cassidy
Andy Clyde
as California Carlson
Ellanora Needles
as Sharon Longstreet
Bobby Larson
as Bobby Longstreet
Victor Jory
as Dan Slack
Jay Kirby
as Johnny Travers
Forbes Murray
as Bart Gailey
Christian Rub
as Sooky Withers
George Givot
as Sam Bucktoe
George Reeves
as Harrison Brooke
Hal Taliaferro
as Telegrapher Lafe
Bill Nestell
as Bartender
