 The 24th entry in the "Hopalong Cassidy" series finds Cassidy visiting a foreign country, other than Mexico which he frequently frequented, for the first time. He would later take a herd of horses to the Middle East: Wealthy Argentine cattle raiser, Jose Valdez (Pedro de Cordoba), buys a prize herd from New Mexico s Bar 20 Ranch (sometimes located in Texas, Wyoming or Arizona in other Cassidy films) on the condition that foreman Hopalong Cassidy (William Boyd) deliver it himself to the Valdez ranch on the Argentine pampas. Hoppy agrees and takes along his saddlemate Lucky Jenkins (Russell Hayden.) Once there, Hoppy becomes friends with all members of the Valdez household, with the exception of his American son-in-law Ralph Merritt (Sidney Blackmer.) Valdez explains Merritt s "moodiness" as caused by the shock of the recent mysterious deaths of both Merritt s wife, and also her brother. The unexplained deaths of Valdez  son and daughter give Hoppy his first clue as to Merritt s true character, as does his friendship with a couple of toughs, Slim (Glenn Strange) and Curly (Eddie Dean), and his interest in a firey dance hall girl, Chiquita (Steffi Duna.) It soon becomes evident to Hoppy that Merritt had his wife and brother-in-law murdered in the hopes of inheriting the vast Valdez estate. Hoppy, aided by Fernando Ramirez (Sidney Toler), acts quickly to save the lives of Valdez and his young grandson, Ernesto/Tito (Jo Jo La Savio), the only remaining obstacles to Merritt s plan. When Merritt and his henchmen make a move to kill Hoppy and Lucky, the fight comes out into the open. Rounding up the loyal gauchos of the Valdez ranch and forming them into a posse, the battle, fought on the pampas and finally on the ranch, begins. Note: the film credits and the pressbook name Strange and Dean as "Schultz" and "Naples", identified as European hired killers in the synopsis, but they are Americanized to just plain American-type henchmen "Slim" and "Curly" in the film itself.