Doctor: David Tennant (Tenth Doctor)
Companion: Catherine Tate (Donna Noble)
Sarah Parish – Empress
Don Gilet – Lance Bennett
Howard Attfield – Geoff Noble
Jacqueline King – Sylvia Noble
Trevor Georges – Vicar
Rhodri Meilir – Rhodri
Krystal Archer – Nerys
Zafirah Boateng – Little Girl
Paul Kasey – Robot Santa
Directed by Euros Lyn
Written by Russell T Davies
Script editor Simon Winstone
Produced by Phil Collinson
Executive producer(s) Russell T Davies
Incidental music composer Murray Gold
Production code 3.X
Length 60 minutes
Originally broadcast 25 December 2006
The Doctor, still saddened by the loss of his companion Rose Tyler, is shocked when Donna Noble, in a wedding dress, appears within the TARDIS while in flight, a near impossibility. She angrily demands to be returned to her wedding as the Doctor performs several tests on her before materialising the TARDIS on Earth, though across the city from the ceremony. Donna leaves in a huff and takes a cab, but the Doctor observes a robotic Santa Claus is driving the cab, and suspects she is being abducted. He uses the TARDIS to rescue Donna from the cab, gives her a ring that masks her presence from other robotic Santas, and escorts her to her wedding, where Donna's family, friends, and groom-to-be Lance Bennett are relieved to have her back. The Doctor examines the video footage of the ceremony, observing how Donna had disappeared, and determines she must have absorbed a great deal of huon particles that drew her to the TARDIS. The ring is unable to mask the huon particles, and soon the reception is attacked by more Santas. The Doctor uses the reception's sound system to disrupt the Santas' control signal, and traces it to a craft in earth's orbit, but loses track of it.
Learning that Donna and Lance work for the Torchwood Institute, the Doctor asks Lance to take them there. Underneath the building the Doctor finds a long tunnel under the Thames Barrier, and a secret laboratory producing huon particles, along with a pit that leads to the center of the Earth. Their presence brings forth the Empress of the Racnoss, a spider-like species wiped out eons ago by the Time Lords, from the pit. The Empress has used the Torchwood company to gain the equipment to make huon particles, and which Lance, who has been working for her, has been feeding to Donna purposely so that Donna may help free the Empress' children. Donna and the Doctor escape, and the Empress decides to use Lance as a substitute, force-feeding him huon particles and then throwing him into the pit.
The Racnoss as shown at the Doctor Who Experience.
The Doctor takes Donna to his TARDIS and travels back billions of years to discover than an inert Racnoss ship became the core of the Earth as the planet formed around it; the Empress is now trying to wake her children aboard that ship with the huon particles. Returning to the presence, the Doctor and Donna return to the Empress to try to stop her, but it is too late, as other Racnoss start emerging from the pit. The Empress brings her ship in orbit towards Earth, firing upon the populace. The Doctor attempts to offer a peaceful solution but the Empress refuses, and the Doctor is then forced to reveal he is a Time Lord and cannot let the Racnoss live. He detonates an explosive he set earlier, flooding the tunnel with water from the Thames, washing the Racnoss back into the pit. The Doctor is prepared to die with the Empress, but Donna urges him to escape with her, just as the Empress teleports to her ship to try to escape. However, this has weakened its defenses, and the ship is destroyed by human forces acting on behalf of Mr. Saxon's. The Doctor returns Donna home, and offers her the opportunity to travel with him. She declines, but does suggest he needs a companion to keep his temperament in check. The Doctor leaves along on his TARDIS.