The program was an adventure series about Sergeant William Preston of the Northwest Mounted Police and his lead sled dog, Yukon King, as they fought evildoers in the Northern wilderness during the Gold Rush of the 1890s. Preston, according to radio historian Jim Harmon, first joined the Mounties to capture his father’s killer, and when he was successful, he was promoted to Sergeant. Preston worked under the command of Inspector Conrad, and in the early years was often assisted by a French-Canadian guide named Pierre.