The Body-Swapper

M.O.M. and Diana decide to break Martin of his habit of always borrowing their stuff. But that is soon overshadowed by problems at the Center's base in the Canadian Arctic where Martin has the choice of co-operating with his old rival Marvin, (who blames Martin for his transfer to the frozen tundra), or becoming a host for the bodysnatching creature that has been accidentally unearthed and is growing stronger with every host it takes.