River's End.

Sgt. Conniston and his alcoholic guide O'Toole are on the trail of an escaped murderer named Keith. When they catch up with him in the farthest reaches of Northern Canada, Keith turns out to be a dead ringer for Conniston. On the way back, the sled overturns, Keith grabs the gun and leaves them to die in the snow. After second thoughts he comes back and brings them to safety at an RCMP emergency cabin. Conniston dies of a frozen lung and Keith takes his place.