The Doctor heals his body but is able to put the rest of his regeneration energy into his hand, so he doesn't change into another person. The Daleks find the Tardis and bring it to their ship. With everyone out of the Tardis except Donna, the Daleks try to destroy it. But when Donna touches the Doctor's hand a human version of him grows out of it and saves the Tardis from destruction. Martha has reached Germany and activates one of the Osterhagen stations. Sarah Jane, Mickey and Jackie are on board the Dalek ship and are barely able to escape the Reality bomb. There they meet Jack and try to destroy the Daleks. But the Daleks are able to bring all of them to the vault. They haven't expected to see the human Doctor and Donna appear out of nowhere and suddenly Donna turns into a human Time Lord. Together they manage to defeat the Daleks and bring all the planets home. The human Doctor destroys all the Daleks, a thing the Doctor wouldn't have done. After the Earth is at it's normal place, the Doctor says goodbye to his companions and leaves the human Doctor with Rose in the parallel world. Is there a future for him and Donna?
This is such a beautiful and, at the same time, sad ending for a series. We have all of the (mostly new) companions of the Doctor in one episode and we even have a human Doctor that grew out of Ten's hand. I Don't think that Davros is right that the Doctor has turned his companions into weapons because the creator of the Daleks just doesn't know what people do for each other when they love someone. It was a great surprise that Dalek Caan helped the Doctor and that he was the one who brought Donna to all the right places, so she was able to save the universe. It's so cool to finally see why Donna is so special and she makes a great Time Lord. Then there are the sad goodbye scenes where all the companions leave the Doctor and get back to their own lives. Rose now has a chance to grow old with the human Doctor but it's sad nonetheless that we probably won't see her again. The most heartbreaking moment is when the Doctor has to take away Donna's memories because she would die otherwise and now he has to travel alone once more.