The Fires of Pompeii

The Doctor and Donna Noble arrive in what the Doctor believes to be Rome in the first century AD. After an earthquake and witnessing a nearby mountain begin to smoulder, he realises he has in fact materialised in Pompeii on 23 August, AD 79, one day before the eruption of Mount Vesuvius. When he and Donna returns to the TARDIS' location, he is told it was sold to a Lucius Caecilius Iucundus, a marble sculptor.
The episode's antagonists are the Pyrovile, giant rock-like creatures resembling golems whose home planet was "lost". They operate secretly; the Sybilline Sisterhood act as their proxies. They use the Sisterhood, which incorporates a high priestess and her acolytes, Spurrina, and Thalina (Lorraine Burroughs), to make prophecies while slowly converting them to stone. The Sisterhood is inducting Caecilius' daughter Evelina and is allied to the local augur Lucius. The Doctor is disturbed by their knowledge of his and Donna's personal lives, and by Lucius' latest commission, a marble circuit board.
The Doctor breaks into Lucius' home and discovers that he is creating an energy converter. He is accosted by Lucius, who sends a Pyrovile to kill the Doctor. The confusion allows the Sisterhood to kidnap Donna briefly; the Doctor follows them and frees Donna. They escape into the Sisterhood's hypocaust system and travel into the centre of Mount Vesuvius.
Mount Vesuvius is being used by the Pyrovile to convert the human race to Pyroviles, in an effort to conquer Earth. The Doctor realises the volcano will not erupt if the energy converter is running, and with Donna's encouragement, subsequently switches it off, triggering the eruption of Vesuvius, considering Pompeii's destruction and the death of its population the lesser of two evils. The Doctor attempts to leave, but Donna convinces him to save Caecilius and his family, whom he then takes on board the TARDIS. The family, The Doctor, and Donna then watch Pompeii's destruction from a vantage point. The Doctor assures the family that Pompeii is never forgotten before leaving with Donna. As he watches the destruction, Caecilius comments that it is the wrath of Vulcan and coins the word "volcano" to describe it.
The last scene takes place six months later in Rome. Caecilius' family are shown to be successful: Caecilius is running a profiting business, Evelina has a social life in comparison to her seclusion in Pompeii, and his son Quintus (Francois Pandolfo) has given up the wasteful life he led in Pompeii and is training to become a doctor. Before Quintus leaves, he pays tribute to the family's household gods, whose statues are in the form of the Doctor, Donna and the TARDIS.