The film stars John Payne, Rhonda Fleming, Dennis O'Keefe, Thomas Gomez, Fred Clark and Frank Faylen.

Guns and ammo are being stolen in Corales, so the governor wants the Ranger and the spy, Whitney Randolph (Dennis O'Keefe), to investigate.

While crossing the Rio Grande, they end up held at gunpoint by a woman, Madeline Danzeeger (Rhonda Fleming), whose wagon is stuck.

After helping her, they learn that a former German army officer also named Danzeeger, likely her father, is working with a Mexican general, Liguras (Thomas Gomez), for big money.

Croyden locates the missing munitions at Basil Danzeeger's (Fred Clark) ranch, but foreman Red Hyatt (Frank Faylen) is suspicious of him.