At the house, the Doctor and Donna meet the local augur, Lucius Petrus Dextrus, who has arrived to collect a sculpture he commissioned. The Doctor is intrigued by the sculpture, which resembles a segment of an oversized circuit board. The Doctor wishes to learn more about the sculptures and enlists Caecilius' son Quintus to help him break into Lucius Petrus' house. Inside, the Doctor deduces that the circuits will make an energy converter, but he is caught by Lucius Petrus, who beckons a large stone creature to attack and kill them. The stone creature appears in Caecilius' house and attacks them, but Quintus douses the creature in water and kills it. In the confusion, the Sisterhood kidnap Donna, and the Doctor sets off to rescue her. The Doctor discovers that the Sisterhood are being controlled by the Pyroviles, stony creatures whose home planet of Pyrovilia was lost. The Doctor escapes with Donna into a tunnel that leads into the heart of Mount Vesuvius.