Yukon King's "lame dog" trick helps Sergeant Preston get close enough to reason with Tom Elders, a gentle veterinarian who turned into a rifle-brandishing hermit after apparently being swindled out of his life's savings of $9,000.
After his Eskimo tribe saves two white men from from freezing to death, tribe leader Ooluk vows revenge when the two decide to repay the kindness by stealing furs and assaulting Ooluk's wife and brother.
Sergeant Preston searches rough and uncharted country for a lost party that was delivering a vital Indian treaty, but he is unaware that his "guide" is actually a saboteur who strongly opposes the treaty.
Sergeant Preston and King go on a determined mission to remote Herschel Island after receiving word that violent mutineers from a stranded whaling vessel have virtually enslaved the peaceful Eskimos who inhabit the area in winter.
Sergeant Preston poses as a cheechako in an effort to expose a pair of murderous thieves who dress in eerie all-white outfits to ambush (and frequently kill) would-be prospectors to steal their supplies.
Treachery abounds as a wealthy man's business manager murders a jewel thief in order to obtain the "Eye of Evil", a $100,000 black pearl that was stolen in the U. S. and smuggled into the Yukon in the hope of finding a buyer.
Bank robber Walt Daniels endangers his ex-wife and young son by returning to their home after telling his violence-prone partner Harry Evans that he must meet Daniels there in order to claim a share of the stolen money.
Hyde and henchman Ram intend to take over Walker transport business. Grandpa El and Billy Walker plead for time as selling valuable pups will clear the debt. But violence occurs and Sgt. Preston chases the culprits to the Canadian border.
Two brothers are at odds with each other after the death of their father. Disagreement over a gold mine fuels their fighting. When a charred body is found in their burned cabin, the surviving brother is arrested.
John Fletcher is the victim of attempted murder by partner Borneo in a mine cave in. Sgt Preston is asked by the Fletcher children to investigate. Nirana's Indian friends rescue John and Preston with Yukon King go after the bad guys.
Sgt. Preston is helping Father Michel establish a home for Indian orphans in Gold Flats but trouble is afoot. Brand and Ransom intend to frame Donovan for theft of rival Braddock's poke. Preston, Yukon King, and the children work together to solve the crime.
Sgt. Preston travels to Goldport to discover the source of counterfeit currency. He goes undercover as a prospector and with Yukon King's help starts working on the case which puts his lady friend Sherry in danger.