
On a cattle drive Hoppy, camp cook Windy, companion Lucky, and young Artie Peters encounter an eccentric professor. The professor professes to be searching for the evolutionary missing link, but in reality he is a cattle rustler who uses his dynamite to scatter the cattle in order capture some of them. Hoppy and Bar 20 guys ultimately capture the professor.

William Boyd
Hopalong Cassidy

George 'Gabby' Hayes
Windy Halliday

Russell Hayden
Lucky Jenkins

Nora Lane
Nora Blake

Harry Worth
Horace Hepburn

Lois Wilde
Laura Peters
Billy King
Artie Peters

William Duncan
Buck Peters

Jack Rutherford
Blackie

Ernie Adams
Keno
John Beach
Pete

Ben Corbett
Henchman

Hang 'em High
Hang 'em High

The Tall Men
The Tall Men

The Cowboys
The Cowboys

Song of Old Wyoming
Song of Old Wyoming

Stagecoach War
Stagecoach War

Sinister Journey
Sinister Journey

The Showdown
The Showdown

Riders of the Timberline
Riders of the Timberline

Riders of the Deadline
Riders of the Deadline

False Paradise
False Paradise

Unexpected Guest
Unexpected Guest

Wide Open Town
Wide Open Town