The Master is able to capture the Doctor and Wilfred and when Donna calls her grandfather, he wonders why there is still someone that is not him. When the Master sends his copies after her, he isn't able to kill her because the Doctor has left her with a defence mechanism. The Master discovers that the drumbeat in his head comes from across time but before he can explore that further, Wilfred and the Doctor are rescued by Rossiter and Addams. They take them onto their ship which is in orbit around Earth but the Doctor stops them from leaving. After a broadcast from the Master, who tells them that he found a White-Point Star and that he wants to bring back the Time Lords, the Doctor repairs the ship and races back to Earth. He is too late though and the council of the Time Lords is already on Earth. When the Master tries to take over the Time Lords, Rassilon turns everyone on Earth back to human and suddenly Gallifrey appears in the sky. Wilfred tries to help and releases a man from the control booth but is trapped in there now himself. The Doctor tries to decide whom he shall kill to break the link of the Time Lords to Earth but when he sees his mother he destroys the White-Point Star instead and Gallifrey returns into the Time Lock. Rassilon wants to kill the Doctor but the Master saves his life. When the Doctor thinks everything is over he sees Wilfred in the chamber that will be flooded with radiation any second and he just can't let him die. And so the song of the Tenth Doctor ends.
This episode is a great ending for the Tenth Doctor and it's sad and funny at the same time. We finally know what the drumbeats in the Master's head are and that they were planted there by the Time Lords to bring them back to life. The scene when the Doctor can't decide whom he should kill to save the Earth is a great one and then he has the chance to see his long lost mother again who shows him the solution of his dilemma. I wouldn't have thought that the Master would save the Doctor but I guess that shows that there was still some of the friendship left from their childhood. The scenes between the Doctor and Wilfred are so moving and you just know that the Doctor wouldn't be able to let Wilfred die. When the Doctor says goodbye to all of his friends and companions, you can't help it and be sad but smile a little bit at the same time. Then there are the last words of the Tenth Doctor before he regenerates which make everything worse and then you have this knew Doctor who makes you almost laugh and look forward to knew adventures. A brilliant end for David Tennant's Doctor and a great start for Matt Smith.