While operating the controls on his TARDIS console, The Doctor accidentally transports his former companion Tegan Jovanka on board. Less than happy about her situation, she reluctantly agrees to help when the Doctor reveals that two Sontarans are on board with a powerful vitrox bomb with which they intend to blow up the ship.

The genesis and development of the Sontaran race through the history of the series, as told by some of the actors and production team involved. This specially produced documentary includes contributions from Terrance Dicks, Elisabeth Sladen, Anthony Read, Colin Baker, Nicola Bryant, Bob Baker, Eric Saward and Stuart Fell.