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.
Includes: Hop-a-long Cassidy, The Eagle's Brood, Bar 20 Rides Again, Call of the Prairie, Three on the Trail, Heart of the West, Hopalong Cassidy Returns, Trail Dust, Borderland, Hills of Old Wyoming, North of the Rio Grande, Rustlers' Valley, Hopalong Rides Again, Texas Trail, Partners of the Plains, Cassidy of Bar 20, Heart of Arizona, Bar 20 Justice, Pride of the West, In Old Mexico, The Frontiersmen, Sunset Trail, Silver on the Sage, Renegade Trail, Range War, Law of the Pampas, Santa Fe Marshal, The Showdown, Hidden Gold, Stagecoach War, Three Men from Texas, Doomed Caravan, In Old Colorado, Border Vigilantes, Pirates on Horseback, Wide Open Town, Riders of the Timberline, Stick to Your Guns, Twilight on the Trail, Outlaws of the Desert, Secret of the Wastelands, Lost Canyon, Undercover Man, Hoppy Serves a Writ, Border Patrol, Leather Burners, Colt Comrades, Bar 20, False Colors, Riders of the Deadline, Texas Masquerade, Lumberjack, Mystery Man, Forty Thieves, The Devil's Playground, Fool's Gold, Unexpected Guest, Dangerous Venture, The Marauders, Hoppy's Holiday, Silent Conflict, The Dead Don't Dream, Sinister Journey, Borrowed Trouble, False Paradise, Strange Gamble
