Serial: 7G  Episode Nos. 673, 674, and 675.  Title: Dragonfire

The Doctor goes hunting for a dragon's treasure, rumored to be somewhere in the depths of Iceworld, a space trading colony on the frozen side of Svartos.  What he doesn't know is that his search is being monitored by Kane, the criminal ruler of Iceworld, who seeks the treasure for a sinister purpose....

This story marks the departure of Bonnie Langford as Melanie and the debut of Sophie Aldred as Ace.

starring Sylvester McCoy as the Doctor, Bonnie Langford as Melanie, Sophie Aldred as Ace, and Tony Selby as Glitz. Written by Ian Briggs, Produced by John Nathan-Turner, and Directed by Chris Clough.

Originally transmitted from 23 November 1987 to 7 December 1987 on BBC1.