Set after The Mutants. Beleaguered by radiation phenomena and an unexplained death in the swamps of the nuclear Savannah River Plant, UNIT U.S.A.'s tiny force of men calls for help from London. In no time, the Doctor, Jo, and the other members of the team are on their way to South Carolina to lead an investigation. But conspiracy, personal ambition, and a dangerous extra-terrestrial creature and its keepers await them. Four Episodes