Col. Ranald Mackenzie is given authorization by the government to operate a covert band of raiders who can cross the Rio Grande River into Mexico to capture bandits who have been taking refuge there. Mackenzie's raiders go deep into Mexico to capture the Bundy gang.; When Lt. Gibbons is killed while investigating a counterfeiting ring based in Mexico, he leaves behind a post card with a cryptic number "32" on it. Col. Mackenzie and Lt. Winters, along with Gibbons' son Ben, go to Rosales to check out the slim clue.; Mackenzie and Winters find two men, disguised as cavalry troopers, who have been running guns.