At dawn the Doctor is found by a party of the Marine Space Corps; they take him to their ship, which has been stranded by a power drain. They are on an expedition to mine "Parrinium" – a mineral abundant only on Exxilon – which can cure and give immunity from a deadly space plague. If the expedition does not leave the planet with a supply of Parrinium within a month then millions will die. They show the Doctor photos of the nearby city – which the Exxilons worship, sacrificing anyone who ventures too close. Sarah does so and is captured and taken to the Exxilons' caves to be sacrificed by their High Priest.