"The End of Time" was aired in two parts. They were a Christmas Special for 2009 and a New Years Special for 2010. It marked the final appearance of David Tennants Tenth Doctor on Doctor Who. Including the supporting cast, it starred David Tennant as The Doctor, John Simm as The Master, Bernard Cribbins as Wilfred Mott and Timothy Dalton as Rassilon. It also marked the return of numerous companions of The Doctor's, including Donna Noble, Sylvia Noble, Rose Tyler, Jackie Tyler, Jack Harkness, Martha Jones, Mickey Smith, Sarah Jane Smith, Luke Smith and Midshipman Alonso Frame, portrayed by their respected actors. With the departure of David Tennant as The Doctor, Matt Smith was chosen as the new Doctor. His first scene came at the end of Part Two, which was a monologue on his part. This character was also given a musical track for his first appearance, which would have parts of it remodelled and turned into his own theme for his first official series. This Doctor would go on past the 50th Anniversary of Doctor Who in 2013.
Plot
Part One
The Doctor learns from the psychic alien Ood that his archnemesis the Master will shortly return, heralding "the end of Time itself". On present day Earth, a cult loyal to the Master attempt to resurrect him; the Master's ex-wife, Lucy Saxon sabotages the ceremony however, and the Master is brought back suffering from constant hunger, also having gained superhuman strength and speed along with energy projection from his constantly expending energy. The Doctor attempts to trace the Master, on Christmas Eve, and encounters his friend Wilfred Mott, to whom the Doctor explains a prophecy that he is to die soon. The Doctor tracks the Master to wastelands outside of London, where the Master subdues him and forces him to listen to the sound of drums in his head. The Doctor discovers that the sound is not a symptom of the Master's insanity, but before he can learn more, the Master is abducted by troops and placed in the custody of billionaire Joshua Naismith.
Wilfred is repeatedly warned by an apparitional woman in white claiming an old service pistol to protect the Doctor, before he is joining him in his time machine, the TARDIS (Time and Relative Dimensions in Space). They travel to the Naismith estate where they discover Naismith is in possession of an alien "Immortality Gate" and has enlisted the Master to fix its programming. Aliens of the Vincocci species reveal themselves and attempt to explain that the device is a simple medical device from their homeworld, but are unsuccessful. The Master ultimately uses the device to replace all of humankind with his DNA, creating a 'Master Race'; exceptions to this are Wilf, who is shielded from its effects, and Wilf's granddaughter Donna, a former companion and friend of the Doctor who acquired Time Lord biological traits in an earlier adventure. The Master and his race taunt the Doctor, who can only look on in horror.
Far across the Universe, the episode's narrator remarks that the Master's removal of humanity is only the beginning of far greater events; the narrator is revealed to be the Lord President of the Time Lords—the Doctor and Master's species— who addresses a vast chamber full of other Time Lords, and announces that it is "the day the Time Lords returned. For Gallifrey! For victory! For the end of Time itself!"
Part Two
The Doctor and Wilfred are rescued from the Master by the Vinvocci, taking refuge on their orbiting ship. Meanwhile, the Time Lord President receives a prophecy about the future after the Time War, and so schemes to use the Master to one day escape. They are able to put a signal in the young Master's head as a small child, creating the drum beat he has heard all his life. When the Master clones himself billions of times, the Time Lord President also sends a "whitepoint star" from their home planet Gallifrey to the Master in the present day to strengthen the connection between present-day Earth and Gallifrey, which presently is "timelocked" in the middle of a Time War shortly before its destruction, a fate which it is otherwise unable to escape. Gallifrey materialises above Earth, and all the other horrors of the Time War are likely to follow. The Doctor, armed with Wilfred's gun, breaks into the room from above, but vacillates over whether to kill the Master or the President in order to sever the link; he eventually spots the whitepoint star and shoots it instead. As he does this, he catches sight of and recognises the woman in white from earlier, and is saddened. As the Time Lords are drawn back into the Time Lock, the President—whom the Doctor names, at the last minute, as Rassilon—attempts to kill the Doctor, but the Master intervenes, sacrificing himself in an act of revenge against Rassilon. In a flash of light, the Time Lords, the Master, and Gallifrey all disappear. Taking a moment to realise his victory, the Doctor hears four knocks, the sound which he has been told will precede his death. He finds Wilfred, having returned to help the Doctor, still trapped in the Gate's isolation chamber that will be flooded with radiation due to the Master's modifications; only the self-sacrifice of another will free him. The Doctor releases Wilfred, collapsing in agony as he receives a massive dose of radiation. Although he survives initially as his body absorbs the radiation, the healing of the Doctor's wounds shows his regeneration process has begun, which means he will soon change appearance and personality.
After taking Wilfred home, the Doctor somberly visits past companions and acquaintances. Companions Martha Jones and Mickey Smith have married and are working as freelance alien hunters; the Doctor saves them from a Sontaran Sniper. The Doctor rescues Luke Smith from an oncoming car, and silently acknowledges Luke's mother, former companion Sarah Jane Smith. At an extraterrestrial bar, the Doctor passes a note to a despondent Captain Jack Harkness, encouraging him to start a conversation with Midshipman Alonso Frame seated next to him. The Doctor appears at a book-signing by Verity Newman, the great-granddaughter of Joan Redfern and asks whether Joan was happy. Newman's book, A Journal of Impossible Things, is based on Joan's diaries, concerning her earlier love affair with the Doctor. He then attends Donna's wedding, and gives her a winning lottery ticket bought with money borrowed from Donna's deceased father to assure their financial future. Finally, the Doctor visits Rose Tyler on New Year's Day 2005, the year when she meets him. He tells her she will have a great year. As the Doctor struggles towards the TARDIS, Ood Sigma appears before the Doctor, and tells him the universe will sing him to sleep and that "this song is ending, but the story never ends". The Doctor says "I don't want to go", and the violent energy his body releases as he transforms shatters the TARDIS windows and sets the console room ablaze. With his regeneration complete, the Eleventh Doctor, a bit dazed and funny in the head, inspects his new body, putting a personal inventory before realizing that the TARDIS is hurtling back to Earth, on New Years Day, 1996.