When a Nestene Energy Unit is stolen and a radio telescope sabotaged, the Doctor is contacted by a Time Lord who tells him his old rival the Master is responsible.
Quest roles:
Richard Franklin(Mike Yates), Nicholas Courtney(Brig. Lethbridge-Stewart), John Levene(Sergeant Benton), Harry Towb(McDermott), Michael Wisher(Daleks (voice)), Dave Carter(Roundhead Officer), Roger Delgado(The Master), Christopher Burgess(Professor Philips), John Baskcomb(Rossini), David Garth(Time Lord), Andrew Staines(Captain)