A handful of courageous men, women, and children locked in the boundless snows of the North were suddently cought in the grip of diphtheria. Only serum could save them. When hope was almost abandoned, Jim Thorne and Silver Chief arrives with the precious life-saving serum. The little outpost was saved. With the arrival of the Mountie and his stalwart dog, the luck of the community seemed to change. Drifting herds of caribou cast their shadows over the wastes, bringing rich game and nourishing food. Then came the fox, which meant priceless skins and a season of plenty. But mysteriously the skins of the fur-trappers were vanishing out of the traps, and none other than Silver Chief was blamed. Jim Thorne set out to clear Silver Chief's name, and his investigation led him throuhg many dangers and surprises.