The Doctor (Peter Davison) is used to life-or-death situations, but is he prepared for an assassination plot involving the Black Guardian (Valentine Dyall) and a seemingly benign student (Mark Strickson) who's really an alien in exile ... and is willing to kill if it means he can go home? A 1980s-era blast from the Doctor's past, this story arc features the first return of fan-favorite villain the Black Guardian since the late 1970s.