The dog, Rex, finds the baby abandoned in the mountains. Unfortunately, the nearest town has no orphanage and rough cowboy and wonder-dog owner Bruce is forced to care for the infant himself.

Wonder dog and horse belong to Pattie, the "wild girl" of the title, who rejects a proposal from uncouth mountaineer Lige Blew in favor of romancing handsome photographer Billy Woodruff. Taking umbrage to the girl's decision, Lige frames Pattie's granddad for murder.

Lovely Jessie Stevens falls in love with Jim Sullivan, much to the dismay of Red Collins (L.J. O'Connor), who wants the girl for himself. Red blackmails Jessie's father, Job, into ordering his daughter to forget all about Jim, who takes to the bottle instead.

In order to save lovely Lorraine from a gang of claim jumpers Art teams with his wonder dog and horse.