The third in the series. This time Bucks son BJ and old Foster are with him looking in Mexico to find who has been selling rifles to the Apaches. This time they are undercover for the government. They find an Apache staked out on an anthill. He helps them find the men responsible with In and out dangers throughout. BJ saves a young woman from the clutches of the bad guys. Once caught the desperados escape and head to take revenge on Buck and the town of Durango. No lack of excitement.