The Doctor gives Rose a choice - backwards or forwards in time. 100 years later - no, 10,000 years, no, wait - 5 billion years. This is the day the sun expands and the world ends.
Well, at least humans haven't all killed themselves in that time.
Aliens are coming to watch the spectacle. They almost get thrown out, but the Doctor has a psychic paper and the blue host decides it's an invitation. The Doctor flirts with a tree. And then they bring out the last human - who is like, the thinnest human possible. Skin stretched in a frame. She is eyeballs and a mouth. Creepy. You can see through her.
These black robe types give everyone a sphere. The tree chick tries to find out the Doctor's species and then says "it's impossible". I'm guessing that's not good.
Rose, meanwhile, watches the end of the world. Is it any wonder she's a little upset. She realizes she has no idea who the Doctor is while talking to a blue skinned alien. The blue skinned alien crawls into a jeffries tube and has an encounter with a spider thing. Or two. Billion. Scream.
The black robed aliens' silver balls may be responsible. They hatch little spider things. Hmmm...
Rose is sitting around playing with hers. She speaks to the plant the tree lady gave her when her little silver ball hatches. Yikes.
The Doctor gets his phone booth valet parked. Then he finds Rose sitting alone. She's trying to deal with the aliens. And then the Doctor won't even tell her who he is. They have a small fight about it. She gets over it. The Doctor rigs her phone so she can phone home.
The station shakes. The blue host guy finds the spider guys but one kills him before he can do anything about it.
They return to the party, and the Doctor and his tree girlfriend go check out why the station shook.
Rose goes to talk to the last human - Cassandra, who used to be a little boy. Cassandra is the last "pure" human - the others interbred with aliens. Rose gets mad and stomps out and the black robed aliens watch.
The tree tells the Doctor she knows where he's from. She says it's remarkable he exists and how sorry she is. He sheds a single tear.
They emerge in the room from Star Trek: Nemesis where Riker and the Viceroy had that big fight.
Rose gets mugged and dragged away by the black robed aliens.
Doctor and the tree discover that there's sabotage. Good on them, everyone else has known for ten minutes.
Cassandra turns on a "traditional ballad" for the end of the world - Britney Spears.
Rose wakes up in a room where the sun filter is descending. Not good.
The Doctor saves her just in time, and the tree tells eveyone what's up. The figure out that the robey types set them. Oh, no, those are just more robots. Turns out it was Cassandra. Just when you think she's won - well, she kind of wins. In the sense of turning off the forcefields and teleporting away.
Of course, the switch is on the other side of a huge fan. Doctor's about to run through it as a hopeless cause when the tree saves him by slowing down the fans at the cost of her own life - she calls him Time Lord, by the way. Anyway, it's about to be very bad for everyone and then the tree dies, which doesn't help. But the Doctor somehow gets through the fan and raises the shield just in time for Earth to blow up spectacularly.
The Doctor brings Cassandra back... and she dries out and dies. Which is gross.
The guests all leave. Rose stays to watch the debris of the Earth. The Doctor takes her away, back to her own century. And then he tells her his own planet is gone - before it's time. He says there was a war, and they lost. His people are the Time Lords and he is the only survivor.
She takes him out for chips, which I think are fries.
It's inside my brain?
Well, in a good way.
-Rose and The Doctor