A ship containing four Daleks arrives; both the ship and their weapons have been rendered useless by the energy drain. The Daleks encounter the Doctor and attempt to exterminate him, but their weapons do not work. The Daleks claim that several of their planetary colonies are suffering from plague; thus they need Parrinium for the same reason as the humans. The Daleks, the Doctor, and the humans form an uneasy alliance to obtain Parrinium and escape Exxilon. While the allies are making their way to the humans' mining dome, the Exxilons ambush them. A massive battle ensues and the Exxilons end up killing a human and a Dalek and capturing the others. The prisoners are taken to the Exxilon caves where the Doctor interrupts Sarah Jane's sacrifice; therefore, he is also condemned to death. When the dual sacrifice commences, a second party of Daleks, who have replaced their energy weapons with firearms, attack in force, killing a number of Exxilons. They force the Exxilons and humans to mine Parrinium. The Doctor and Sarah flee into tunnels. The other party of Daleks arrive and they discuss their actual plan to use Parrinium to create a plague and spread it across every planet except their own.