The Darksmiths have the Eternity Crystal and are eager to finally fulfil their contract with their mysterious client.
The Darksmiths have also reprogrammed Gisella, the robotic 'daughter' of Varlos, who now seems to be working for them.
The Doctor learns that the Darksmiths are due to hand over the Crystal to their client as a secret rendezvous on present day Earth.
Will the Doctor be able to intercept the transaction in time? Or will the Crystal begin a war that will continue for all eternity?