Lucifer Rising

"If I'd wanted to spend the rest of my life hoofing it around grimy spaceships for no good reason I'd have stayed in Spacefleet." Ace is back. And she is not in a good mood. Bernice has asked the Doctor to bring the TARDIS to the planet Lucifer, site of a scientific expedition. It's history to her: the exploration of alien artefacts on Lucifer came to an abrupt halt three centuries before she was born, and she's always wondered why. Uncovering the answer involves the Doctor, Bernice and Ace in sabotage, murder, and the resurrection of eons-old alien powers. Are there Angels on Lucifer? And what does it all have to do with Ace?