The Doctor has escaped the catastrophic destruction of a parallel world. But can he stop Stahlman before he destroys this one?
Quest roles:
Nicholas Courtney(Brig. Lethbridge-Stewart), Derek Newark(Greg Sutton), Terry Walsh(Doran (uncredited)), John Levene(Sergeant Benton), Sheila Dunn(Petra Williams), Ian Fairbairn(Doctor Chester), Olaf Pooley(Stahlman), Christopher Benjamin(Jago)