The BBC Press Office have released the synopsis on both parts of Doctor Who: The End of Time:
PART 1 - Christmas Day, 6:00pm
It's the Tenth Doctor's final journey - but his psychotic nemesis the Master has been reborn, on Christmas Eve. With both determined to cheat death, the battle ranges from the wastelands of London to the mysterious Immortality Gate, while the alien Ood warn of an even greater danger approaching, as a terrible shadow falls across the entire Universe.
PART 2 - New Year's Day, 6:40pm
The Doctor faces the end of his life as the Master's plans hurtle out of control. With the sound of drums growing louder, and an ancient trap closing around the Earth, the Doctor and Wilf must fight alone. But sacrifices must be made, and the deadly prophecy warns: "He will knock four times."
Both episodes will broadcast on BBC One and BBC HD. In other news: Today marks the 46th anniversary of Doctor Who! The show began back in 1963 on Saturday 23th November, since then, over 200 stories have been broadcast.