In this 15-episode serial starring Rin Tin Tin, Rinty's owner is murdered for his secret gold mine, and Rinty teams up with Agent Ramon (Walter Miller) from the Department of Justice to help find the culprit. But Rinty soon joins the ranks of the suspects when he is accused of killing a prized colt, and it is up to Agent Ramon and his sidekick, Buzz, to rescue Rinty from the clutches of the killer, who has since kidnapped the canine.