Following the events of the previous episode, Rose and the Doctor are in the TARDIS, with endless possibilities ahead of them as a destination. When Rose wishes to see the future, the Doctor takes her five billion years further, to a space station from which Earth can be seen. In the meantime, the sun has completed its life cycle and will burn up and destroy the earth in a short time. Humanity has long since left its planet and scattered and evolved all over the galaxy.
To celebrate the end of the Earth, an exclusive farewell party is to take place on board the space station, to which the doctor invites himself and Rose with the help of the mind-manipulating paper. The other guests include the face of Boe, Jabe (the emissary of the trees) and Cassandra O'Brien, who calls herself the last (pure-blood) human. However, Cassandra is now only her skin with face stretched into a frame. In order not to dry out, she has to be constantly moistened.
Rose, meanwhile, is overwhelmed by what she sees: the aliens, the space station with its technology and the impending end of her world. From this perspective, everything she knew and every person in her life is already long dead and lost. Her own life suddenly seems insignificant. She becomes homesick. The doctor notices her despair and allows her to call home to the past. But that doesn't seem to help either, because now she wonders who this doctor she is travelling with actually is. After all, he hardly reveals anything about himself.
Suddenly, however, the situation changes and the apparent peace is disturbed. The steward in charge of the festivities is murdered by tampering with the radiation shield of his office. Subsequently, a similar murder attempt is made on Rose, but she is saved by the Doctor at the last second. Now he wants to find out who is behind the attacks. Jabe supports him, she seems to have an idea of who and what the Doctor actually is.
They are able to find out that small, spider-like robots were used for the sabotage. The person or persons responsible must also be on the space station. With the help of the robots, the Doctor can expose Cassandra as the assassin. Her plan: destroy everyone on board the station and profit from its demise as the sole survivor. After this revelation, she teleports away.
Now, however, the station is in trouble and the heat shields threaten to fail in the face of the exploding sun. When the situation seems almost hopeless, Jabe sacrifices himself to help the doctor and save the station. Now that everyone else is safe again, the Doctor finds Cassandra's teleportation device and retrieves it. He makes her pay for what she has done by - despite Rose's objections - allowing Cassandra to dry out and burst in a flash due to the temperature.
Back in 2005 London, the Doctor finally reveals to Rose who he is: the last surviving Timelord. His world has long since passed away. Rose, however, makes it clear to him that he is not alone and invites him for fries.
