A human mercenary was taken by an alien along with the SontaranSarg, a Draconian and the commander of the Brigade Merq for experiments. The alien hoped to learn their strengths and weaknesses. The human eventually killed her captor and got herself and her fellow prisoners back where they had came from. (HOMEVID: Mindgame)
In Mindgame, the unnamed human mercenary was strongly implied to be an older version of the Seventh Doctor's companion Ace, likewise played by Aldred. However, her identity was considerably more ambiguous in Mindgame Trilogy, and the fact that the character perished in it further dissociated her with Ace.