The Fires of Pompeii
SPOILER Summary: The Doctor and Donna arrive in what he says is ancient Rome, but an 
earthquake and Mt. Vesuvius tells him this is Pompeii. As the TARDIS has been “sold” to a man named Caecilius. Arriving there to get the TARDIS back, the Doctor and Donna are in time to meet one Dextrus, the town augur, who’s had Caecilius build what looks like a circuit board of marble. They learn that Caecilius’s daughter Evelina (a prophetess set to join the Sibylline Sisterhood) and Dextrus accurately identify the Doctor as being from Gallifrey and a Lord of Time. With Donna wanting to save the people of Pompeii (something the Doctor refuses to do) and not taking no for an answer, the Doctor pays the Sibylline Sisterhood a visit, to discover their chief priestess turned to stone and 
being possessed by someone from the race known as Pyrovile (a stone people). Going underground, the Doctor and Donna discover the stranded Pyrovile, who want to make Earth their new home. Given the choice of 20,000 deaths vs. the entire world, Donna finally understands and they throw the switch to destroy Pompeii (causing Vesuvius to errupt). Donna asks the Doctor to save at least one person, so he saves Caecilius’s family as that won’t change history.
Thoughts: This was a pretty good episode, more so than last week’s for sure. I understand Donna wanting to save Pompeii because that is an emotional response. Her argument for the 
Doctor saving Earth when he met her the first time is a reasonable one. I liked how the writers tied the destruction of Pompeii back to the loss of Gallifrey and how the Doctor cannot (apparently) change that outcome either. Donna, while still being a mule head at times, is still much better than she was in the Christmas special with her deciding to help the Doctor throw the switch to destroy Pompeii. I liked that as well.
The joke about the TARDIS translator and Donna trying to speak Latin to the Romans at Pompeii was amusing. However, I figure that IF Donna actually knew Latin, the translator wouldn’t be required, would it? She should be able to speak and the other people understand her. So while the joke is amusing, it doesn’t make a lot of sense to me in a “realistic” sense (given that this is a work of fiction).
The whole “Doctor is a deity” thing came up again. It is not an aspect I’m that keen on, but it is interesting to say the least.