Heart of the Rockies

The Three Mesquiteers--Stony Brooke, Tucson Smith and Lullaby Joslin--find trapper Enoch Dawson on their ranch and accuse him of being behind their recent cattle losses. Enoch explains that he was on his way to the nearby Blackstone National Park, where the bears that have been killing the Mesquiteers' cattle live. After Enoch shows them bear tracks surrounding a cow skull, the Mesquiteers decide to do some bear hunting. They enter the park, but are stopped by park ranger Brady and warned that they cannot bring guns into the preserve. The disgruntled Mesquiteers go to the cabin of Enoch's father, Big Ed Dawson, and suggest that the Dawson clan kill bears for them. While Lullaby plays with Davey, Ed's young stepson, and the wild animals Davey has rescued from the traps, Stony and Tucson discover that Ed intends to marry his teenaged stepdaughter Lorna to Charley Coe, an uncouth older man. Lorna and her mother have been terrorized into agreeing to the ceremony, but the Mesquiteers stop it by telling Ed that Lorna cannot be legally married until she is sixteen. After the Mesquiteers leave, Ed warns the youngsters not to tell about the cattle he and Enoch have been rustling, or else he will beat their mother. Time passes as the Dawsons kill the park's bears and continue rustling the ranchers' cattle. One day, Ed forces Davey to run a line of traps into the park, where the boy falls off a cliff onto a ledge. The Mesquiteers rescue Davey, who has a broken leg, from a mountain lion about to spring onto the ledge. Later, the Mesquiteers again see bear tracks around one of their dead cows, but they also see another, strange track. They realize that it is from Davey's crutch, and that the bear tracks belong to Davey's pet bear Nero. The friends go to the Dawson cabin, where Lorna tearfully tells them that Ed intends to force her to marry Charley soon. While Stony and Enoch fight over the matter, Lullaby takes a plaster cast of Nero's foot and discovers that his prints match the others. After Stony trounces Enoch, he orders Ed to keep Charley away from Lorna. The Mesquiteers then set a trap for Ed by asking him to look after their stock while they are gone. Later that day, Ed orders Ma Dawson to pack up while he and Enoch make one last roundup of the cattle. Enoch forces Davey to bring Nero, but the Mesquiteers spring their trap. Enoch and Ed escape, and while Tucson and Lullaby chase them, Stony chases Charley. Stony and Charley are captured by Brady, whom Charley shoots in the back before Stony can explain the situation. Stony is wounded by Charley, but makes it to the cabin, where Lorna hides him in their wagon. The rangers look for Stony, but Lorna keeps him hidden, and he tells her about the murder. Lorna finds Tucson and Lullaby, and after they come to the rescue, the gang is apprehended and ranger Clayton arrests Charley for the murder. Soon after, the children are safe and happily play with Lullaby.