The Doctor and Jo visit the Master at his island prison where the Doctor becomes curious about a number of ships sinking in the area.
Quest roles:
Edwin Richfield(Mestor), Royston Tickner(Robbins), Terry Walsh(Doran (uncredited)), Pat Gorman(Pilot), Roger Delgado(The Master), Clive Morton(Trenchard), Neil Seiler(Radio Operator), Declan Mulholland(Till), Hugh Futcher(Hickman), Brian Justice(Castle Guard Wilson), Alec Wallis(Warner), June Murphy(3rd Officer Jane Blythe)