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.
Hopalong Cassidy
Windy Halliday
Lucky Jenkins
Nora Blake
Horace Hepburn
Laura Peters
Artie Peters
Buck Peters
Blackie
Keno
Pete
Henchman
Dirk
Bar 20 Cowhand
Henchman
Slim
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