The TARDIS collides with the Titanic. The Doctor (David Tennant) initiates the TARDIS self-repair programme and boards the Titanic, which is a nuclear-powered cruiser from the planet Sto. It is orbiting Earth to observe primitive cultures, i.e., Christmas festivities. The Doctor stows away on board and joins a party, which includes the waitress Astrid Peth (Kylie Minogue), on an observation excursion to London. But the people of London, having been attacked by aliens the last two Christmases, run away from them.
After the party returns, suicidal Captain Hardaker (Geoffrey Palmer) sabotages the ship by collision with three large meteors. Most of the passengers are killed and the ship is drawn into an extinction-level collision with Earth. Midshipman Alonso Frame (Russell Tovey) helps the Doctor stabilise the ship. On the way to the bridge, the Doctor’s party is repeatedly attacked by the Host, who are androids who look like angels but are programmed to kill the survivors.
The Doctor leaves the party and tries for the control point for the Host. The controller of the Host is the former cruise-line owner Max Capricorn (George Costigan)—just a head attached to a mobile life-support unit. Capricorn is angry because he was forced out of his own company, and he arranged for the accidents to bankrupt the company and frame the Board of Directors for murder. Astrid saves the Doctor’s life by ramming Capricorn with a forklift, sending both Capricorn and herself over a ledge to their deaths.
The Doctor uses the Host to reach the bridge and uses the heat from atmospheric entry to restart the ship’s engines. He prevents the ship from crashing into Buckingham Palace. Astrid’s DNA is in her teleport bracelet, but he cannot regenerate her, so he allows her to dissipate into atoms and explore the universe as she always wanted.
The part of Astrid was written specially for Kylie Minogue. Her performance was praised, but the episode itself received mixed reviews. Geoffrey Palmer is well-known to British viewers of movies and TV. He is the go-to performer when a man of lugubrious mien is needed. Bernard Cribbons played London news-vendor Wilfred Mott, later companion Donna Noble’s grandfather. The story was, of course, influenced by The Poseidon Adventure.
The show was dedicated to Verity Lambert, the first producer of Doctor Who, who had just died. David Tennant’s mother died of cancer during the filming and he took time off. Shooting went on around him. Composer Murray Gold and Conductor Ben Foster appeared in the ship’s band. There were complaints about supposed disrespect for the victims of the real Titanic, and about portraying angels as bad guys. But vicars used the image of the Doctor being raised on high by the angels to illustrate themes of resurrection and redemption to young people.