Having already made a successful transition to talkies, canine star Rin-Tin-Tin remained on the Warner Bros. payroll throughout 1930. In On the Border, Rinty plays a police dog living at a lavish California hacienda near the Mexican border. The villainous Farrell (Philo McCullough) decides to use the house as a rendezvous point for his thriving alien-smuggling operation. But Farrell is foiled by Dave (Dave B. Litel), a border cop posing as a bum, and (of course) by Rin-Tin-Tin. The femme lead is played by Mexican song-and-dancer Armida, some ten years before she was "officially" discovered by Hollywood.