Sergeant Preston offers help to an inexperienced young couple while pursuing thieves who have tapped into the RCMP's telegraph line in order to obtain confidential information concerning gold shipments. Directed by: Alan Crosland Jr. Writers: Dan Beattie, Robert C. Bennett, Fran Striker, George W. Trendle Dick Simmons as Sgt. Preston Yukon King as The Dog Rex as The Horse Don Durant as Jack Flynn Maggie Magennis as Lindy Flinn Initially broadcast on January 26, 1956. Canadian Mountie Sgt. Preston patrols the wilds of the Yukon with his horse Rex and his faithful dog Yukon King, battling both the elements and criminals.