The Doctor learns that Styre has been experimenting on the Galsec crewmembers to pave the way for a Sontaran invasion of Earth and decides the only way to halt his plans is to challenge him to a duel.
Quest roles:
Donald Douglas(Vural), Glyn Jones(Krans), Peter Walshe(Erak), Peter Rutherford(Roth), Brian Ellis(Prisoner), Kevin Lindsay(Styre / The Marshal)