Rinty of the Desert (1928)

Rinty (Rin-Tin-Tin), a dog of the desert, wanders into a big city and finds many reasons to turn his back on humanity. He is given a home by sweet June Marlow (Audrey Ferris) but he soon finds himself being treated badly by animal trainer Mike Doyle (Paul Panzer). But he saves his mistress from the unwelcome attentions of oily Doyle and then comes to the rescue of June's grandfather ,Pop Marlow (Otto Hoffman), who is being held prisoner by a gang of hooligans.