Watch Doctor Who: The David Tennant Specials

The Doctor Who specials were a link from the fourth to the fifth series. There were four specials: "The Next Doctor," "The Planet of the Dead," "The Waters of Mars" and the two-part "End of Time." "The Next Doctor" finds the Doctor in Victorian London. He discovers the Cybermen trying to regroup for another attack. He also finds someone who thinks he's the Doctor.

"Planet of the Dead" sends the Doctor and passengers on a London bus through a wormhole. To escape the planet, which has been turned into a desert by aliens, the Doctor needs the help of all the passengers. Back on Earth, Unit is working to save them and close the wormhole before the aliens get through.

In "The Waters of Mars," the Doctor lands near the first Martian base. He finds out what the history books never knew, why the base disappeared. To help save them from the virus attacking the base, the Doctor risks changing history.

"The End of Time, Part One" sees the return of old friends and enemies. The Ood tell the Doctor that the Master is coming back. While searching for him, the Doctor meets up with Wilfred. Together they track the Master to a group who want his help repairing an alien gate. The Master uses this as a way to help himself. All the time, the Master is coming closer to finding out who has been using him for his entire life.

"The End of Time, Part Two" marks the return of the Time Lords and Gallifrey. They used the drumbeats in the Master's head as a signal to escape the Time-Lock they were in. The Doctor is forced to send them back to keep the Time War from happening again. In the end the Master saves the Doctor, who in turn saves Wilfred. Before his regeneration is complete, the Doctor goes on a farewell tour and visits all his previous companions.