While sightseeing in a Mexican town Scott and Robinson think they see someone familiar. When they approach him he gets the drop on them and gets away. After checking they find out that Frank Hunter a convicted mental patient judged incurable and sentenced to life has escaped. Hunter is a demolitions expert who has sworn revenge against Tom Matthews, the agent who apprehended him. Matthews has retired and lives with his family in Mexico. Robinson and Scott are assigned to find Hunter and stop him before he can hurt Matthews and his family.