Doctor: David Tennant (Tenth Doctor)
Companion: Catherine Tate (Donna Noble)
Peter Capaldi – Caecilius
Tracey Childs – Metella
Phil Davis – Lucius
Sasha Behar – Spurrina
Francesca Fowler – Evelina
Lorraine Burroughs – Thalina
Victoria Wicks – High Priestess
Francois Pandolfo – Quintus
Karen Gillan – Soothsayer
Phil Cornwell – Stallholder
Directed by Colin Teague
Written by James Moran
Script editor Brian Minchin
Produced by Phil Collinson
Executive producer(s) Russell T Davies
Incidental music composer Murray Gold
Production code 4.3
Series Series 4
Length 50 minutes
Originally broadcast 12 April 2008
The Doctor and Donna 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 one day before the eruption of Mount Vesuvius. When he and Donna return to where the TARDIS landed, he discovers that a local merchant sold it to sculptor Lobus Caecilius. The Doctor and Donna go to Caecilius's house to retrieve it. Unknown to them, they have been followed by a soothsayer who reports to the Sibylline Sisterhood that the prophesised man in the blue box has arrived, and the Sisters fear the prediction that his arrival brings fire and death.
The circuit prop, on display at the Doctor Who Experience
At the house, the Doctor is surprised by Caecilius's daughter Evelina, who seems to have extrasensory perception (ESP) and knows personal details about the Doctor and Donna. They are interrupted by 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. Lucius Petrus reveals that he also has powerful ESP and calls out the name of the Doctor's home planet, Gallifrey. The Doctor wishes to learn more about the sculptures and enlists Caecilius's 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. The two escape, but Lucius Petrus beckons a large stone creature to attack and kill them. The stone creature appears in Caecilius's house and attacks them, but Quintus saves them by dousing the creature in water and killing it. In the confusion, the Sisterhood kidnap Donna, and the Doctor sets off to rescue her. He meets the high priestess of the Sisterhood, who is revealed to be transforming into a stone creature. The Doctor discovers that they are being controlled by the Pyroviles, volcanic creatures whose home planet of Pyrovilia was lost. The Doctor is attacked by the Sisterhood, but he escapes with Donna into an underground tunnel that leads into the heart of Mount Vesuvius.
The Doctor discovers that the volcano is being used by the Pyroviles to convert the human race and conquer Earth. The Doctor realises the volcano will not erupt if the energy converter is running, and tells Donna that the volcanic eruption is a fixed point in time and must always happen. The Doctor and Donna get into an escape pod and together press a lever which overloads the converter and triggers the eruption, killing the Pyroviles and launching the pod clear of the blast. The Doctor and Donna run for the TARDIS and the Doctor coldly leaves Caecilius and his family cowering in their home using the TARDIS in order to not interfere too deeply with history. However, Donna tearfully begs him to go back and at least save one person, regardless of who it is. The Doctor finally relents and goes back for Caecilius and his family. He leaves them on a hill overlooking the destruction, and together with Donna slips out quietly as the family mourns Pompeii. The Doctor comments to Donna that she was right - he does need someone to stop him.
Six months later in Rome, Caecilius and his family are shown to be successful; he is running a profitable business, Evelina has a social life in comparison to her seclusion in Pompeii, and his son Quintus is studying to become a doctor. Before Quintus leaves, he pays tribute to the family's household gods (in marked contrast to his disrespectful attitude towards them at the start of the episode), a bas relief depiction of which are in the form of the Doctor, Donna and the TARDIS.