The Earth has been conquered, the Master rules supreme, and the Doctor is his prisoner. Can Martha Jones save the world?
Then barbiturates are stolen from Raif and Georgina Canning's veterinary surgery and the district nurse is found in her crashed car in a confused state. Barnaby and Troy dash to the Manor, fearing the drugs theft may be connected to the death threats - but they find Melissa is already lying dead by the swimming pool with a syringe in her stomach. Now they have a murderer to find.