A notorious criminal, "The Fox", is released from prison and seeks revenge against the lawmen who captured him, Colonel Gonzalez and Hoppy. The Fox lures Cassidy to Mexico with a fake letter, killing Gonzalez, and is aided by his sister Janet, who has caught the eye of the chivalrous Hoppy.
In Old Mexico
Notorious outlaw "The Fox" seeks revenge against Hoppy and a Rurales colonel who imprisoned him unfairly, devising a plan to lure Cassidy to Mexico for his vengeance.
