Wow. These episodes are insane. Everyone comes back, and everything happens. But I'll do my best.
The earth is stolen. Literally just removed form orbit and stuck in the middle of a bunch of other planets. Harriet Jones, Former Prime Minister, returns and contacts Martha, Captain Jack, and Sarah Jane (who's weird). Rose watches their conversation. They need to get the Doctor down to earth, but he can't get there because they're stuck in a pocket of time. So they triangulate a phone signal from every phone on earth. The Daleks, who are responsible for this mess, as they are in nearly every season finale up to this point, track the signal to Harriet, and exterminate her. But Torchwood continues the signal, and the Doctor manages to use the signal to take him to earth. Rose leaves to go find him.
They got to see each other. It was so wonderful and happy. David Tennant is such brilliant actor. Anyways, as they were running towards each other, the Doctor got exterminated. He was carried back into the TARDIS by Rose with Mickey and Jackie's help. He regnerated, but transferred his regeneration energy into his decapitated hand, which had, up to this point, sat in a corner of the TARDIS. And he stayed the same.
Martha, meanwhile, is going to Germany to trigger the AusterHagen key (sp? I don't speak German!), which will blow up the earth, and disrupt the Daleks' (really, Davros' ((the creator of the Daleks)) ) weapon which will destroy reality. I won't spoil the ending, but it was really good.
Overall, I really enjoyed these episodes. Really, I really enjoyed this season, once Donna stopped being irritating. It was just such a good season that really framed the finale perfectly. Really. And they resolved the Rose thing perfectly (hint: she doesn't die). It was just so well done, and sad, and it made me cry, especially the part with Donna's Gramps. It was perfect. A little confusing, but perfect.
We've reached the Journey's End
Having a laugh inside the TARDIS.
Though it didn't make much sense,
It's always nice to see them Daleks.
~Journey's End by Chameleon Circuit