'Imperial Moon', written by Christopher Bulis, features the Fifth Doctor, Turlough, and Kamelion.
Back Cover Blurb
The year is 1878. Three ships of the British Imperial Spacefleet have just set course for the moon.
The discovery of a mysterious diary, recalling a seemingly impossible journey, takes the Doctor and his companions back to a crucial moment in history - and into certain danger. For the Moon of 1878 is far from deserted.
Trapped in a crater teeming with hostile animal and plant life, the Doctor and turlough must join the British explorers on a hazardous journey to battle for their freedom before the long lunar night descends. For, lurking in the shadows, are the Vrall - cunning and utterly ruthless killers.
With the loss of one of their ships - and their captain - the British team become embroiled in a struggle to survive that tests duty and honour to their limits. Meanwhile, Turlough finds himself with Time in his hands and the Doctor must make a choice that will determine the future of an Empire - and Earth itself.