As rustled cattle have mysteriously disappeared, Bar 20 ranch hand Johnny Travers sends for old friends Hopalong Cassidy and California Carlson.

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.—Maurice VanAuken <[email protected]>

In order to find out whether ranch owner Dan Slack might also be a cattle rustler, Hoppy gets a job on Slack's ranch. When he is discovered by Slack's crew, he is framed for murder. When Bobby proves Hoppy is innocent, Hoppy finds out Slack is in cahoots with Sam Bucktoe who is using his mine as a place to store the stolen cattle.—Ed Stephan <[email protected]>