Saul Murphy one of "The Adherents" from End of the World
The Doctor takes Rose to five billion years into her future in the TARDIS, landing on "Platform One", a space station in orbit around Earth; the earth has long since been abandoned and kept under the National Trust, but, as money has run out, it is about to be destroyed by the expansion of the Sun, only presently held back by gravity satellites. The Doctor uses "psychic paper" to pass as their invitation to the party, and he and Rose find many elite extraterrestrial beings there to celebrate the end of the earth in the protection of Platform One's automated shields. The guests include Lady Cassandra O'Brien Dot Delta Seventeen, simply a face on a large piece of skin that must be continually moisturised, mounted on a frame with her brain in a jar below it, who calls herself the last human in the universe. Rose is overwhelmed by the strange beings and customs as well as how distant she is from home, and leaves to an observation room to collect her thoughts. The Doctor follows her, and tries to cheer her up by allowing her to call her mum Jackie after altering her mobile phone to be able to work over the distance in time; this however only serves to depress Rose more.
Meanwhile, the gifts brought by the Adherents of the Repeated Meme, small metallic spheres, are revealed to contain robotic spiders that immediately work at disabling functions on Platform One. The Steward of Platform One recognizes something is wrong, but is killed when the spiders cause the solar filter of his room to lower, exposing him directly to the powerful solar radiation. The Doctor goes to investigate with the help of Jabe, a humanoid plant being from the Forest of Cheem, and discover the Steward's death and the spiders. Rose attempts to learn more from Lady Cassandra but only gets more upset over Cassandra's arrogance and walks away, only to be knocked out by members of the Meme. She wakes up in an observation room, the solar shield slowly lowering, and calls for the Doctor to save her. The Doctor finds he can stop and raise the shield, but cannot unlock the observation room, and so turns to the various guests.
The Doctor uses a spider that he captured to determine that while the Meme released them, they are only empty shells, and that the real controller is Lady Cassandra. Cassandra admits to this, and was planning to use the situation as a hostage crisis to get money to pay for her repeated operations, but now plans to simply let the assembled guests die then profit from the stock increases of their competitors when they are dead. Cassandra transmats to her ship as the spiders bring down the shielding and the gravity satellites are turned off; the direct radiation causes the solar filters to strain and crack, killing several of the guests from the intense radiation exposure and leaving Rose to scurry to find shelter in the observation room. The Doctor and Jabe travel to the bowels of Platform One where the system to restore the automated shields is located, though it requires one of them to travel through several spinning fans. Jabe recognizes the Doctor as the last Time Lord after the Time War, and sacrifices herself to hold down a switch to slow down the fan blades, allowing the Doctor to reactivate the system just before the expanding Sun hits the station and destroys Earth.
The Doctor returns to the remaining guests and Rose, free of the observation room, and uses a device to transmat Cassandra back onto the station. In the elevated temperature and without moisturising, Cassandra begins to dry out and crack, and while she begs for mercy from the Doctor, he refuses to listen, and shortly, Cassandra explodes. Rose notes that with all the events that occurred, no one had witnessed the actual destruction of Earth. Returning to Rose's present, the Doctor explains to her that his own planet, Gallifrey, was destroyed in the wake of a great war, that he is the last Time Lord, and that people tend to forget that things do not last forever. Rose sympathises with the Doctor as they enjoy some chips on a sunny London afternoon.