Donna Noble
In the episode, set in London, the alien Racnoss Empress (Sarah Parish) and the human resources head Lance (Don Gilet) attempt to use Lance's fiancée, the secretary Donna Noble (Catherine Tate), as a "key" to awaken the Racnoss children hibernating at the centre of the Earth by gradually and secretly poisoning Donna with an alien particle the Racnoss use as an energy source.