Doctor Who - The Juggernauts

Within a small mining colony on the dark and distant planet of Lethe,
events are occurring the results of which could dramatically affect 
things on a universal scale. For within the dingy corridors of the 
artificial biosphere, the lone survivor of a devastating crash has 
expertly wormed his way into the lives of the colony's personnel. 

A scientist known as Davros. 

Separated from one another across space and time, the Doctor and Mel
find themselves in very different predicaments: Mel has been employed
on Lethe, while the Doctor has been imprisoned aboard an alien spacecraft.
Both situations are inexorably linked, however,and at the apex of the two
sits Davros and the terrifying possibility of a new threat even more 
powerful than the Daleks! 

Rescuing Mel and stopping Davros should be the Doctor¹s primary goals, but
could it be that this time, Mel does not wish to be rescued? And might
Davros actually be working on something for the benefit of the civilised galaxies 

This story takes place between "The Trial of a Time Lord" and "Time and the Rani".