Be forewarned that "Captain (King of Dogs) "and "Dynamite (The Wonder Horse) " are billed above all of the cast except John Preston (who?), which means RCMP Sergeant Bruce Morton (John Preston) is going to spend a lot of time talking to Dynamite (Dynamite the Horse) and Captain (Captain King of Dogs) , and the scary thing is they react better than most of the cast. Inspector Dawson (Harry Beery) promises "Morton of the Mounted" a long-awaited vacation as soon as he solves the mystery of who killed an old fur trapper called Old Dan Parker (Fred Parker) and a Mountie named McGee. Morton and his Mountie sidekick Corporal Tiny Anderson (Tiny Skelton) hit the tundra and Morton, or the dog or the horse or all three, save Mildred Boynton (Myrla Bratton) from a tormentor. She says she and her brother, Bill Boynton (James Sheridan)are staying at a nearby lumber camp and she is worried about Bill as he has become friends with a man named Burke (Tom London) who causes Bill to drink too much. And, besides that, Burke is constantly forcing his unwanted attentions upon her. Morton allows as how he'll try to straighten Bill out when it is obvious Burke needs a little talking to himself. Morton has barely arrived when Burke ambushes him, ties him up and forces Bill, dressed as a Mountie, to go rob the lumber camp pay-roll. Morton, after being rescued by the dual efforts of Captain and Dynamite --- one of them notified the other of Morton's problem --- finally begins to suspect that Burke may be the root of all the problems and takes after him. Bill brings the robbery loot back to Burke, who shows his appreciation by shooting him dead, and Burke takes off. But Morton is not far behind.