AIR DATE: April 14, 2007
ALIENS/ MONSTERS: Macra
OTHER CHARACTERS: Thomas Kincade Brannigan, Novice Hame, Milo, Cheen, Valerie, Alice, May, Sally Calypso, The Face of Boe
LOCATION: New Earth, New New York 5,000,000,053
Sally Calypso gives the daily travel news to all the cars. Ma and Pa are seated in one of the camper-Vans. They call the police for help as they are apparently attacked by something from outside. They are placed on hold by the police computer system, and scream as their car is torn apart.
The Doctor offers Martha one trip into the future, to visit another planet. She asks if he can take her to his home planet, and speculates as to its beauty. He describes Gallifrey's Citadel, mountains, orange sky and other features as if they still existed, but claims he does not want to go home. Instead, he takes her to the year five billion and fifty three, into a dark alleyway where it is raining, and introduces her to New New York in New Earth. The Doctor repeats some things he told Rose the last time he had visited the planet. Martha becomes slightly upset when she realises she is being taken to the same place the Doctor took Rose, and mutters the word "rebound".
Meanwhile, the Face of Boe sits in a room with Novice Hame. He tells her to find the Doctor before it is too late. She takes out a gun and leaves. The Doctor and Martha are in a run-down street. Three pharmacists open their market stands and try to sell the Doctor and Martha patches that dispense "moods". The Doctor is angry, but intrigued when a young girl buys a Forget patch after losing her parents to "the Motorway".
Suddenly, a young couple armed with guns grab Martha and haul her away, subduing her with a patch inducing Sleep. The Doctor chases them but they escape in their car. The Doctor asks the pharmacists for directions to the Motorway; they comply, but warn him that he may never see Martha again. He tells them to find alternative employment as he promises to shut down their enterprises by that very evening.
Martha wakes up and grabs a gun, only to learn it is a fake. Her kidnappers introduce themselves as Milo and Cheen. Cheen says she is pregnant. Milo explains they only wanted her so they could get on the Fast Lane, which requires three adult passengers. They say they can drop her off when they reach their destination - in six years.
The Doctor arrives at the Motorway, where he discovers thousands of Volkswagen-like hover vans in a traffic jam. He starts to cough and choke from the fumes. A cat person invites him into his car, introducing himself as Thomas Kincade Brannigan and his human wife as Valerie. Their kittens, two months old, have never seen sunlight or trod on ground. The Brannigans themselves have been driving for twelve years, and have travelled only five miles.
As Milo, Cheen and Martha head for the Fast Lane, the Doctor calls the Police but is put on hold. Brannigan speaks to some old friends, the Cassini "sisters" (a same-sex married couple), who identify the one car from Pharmacytown that has gone to the Fast Lane. The Doctor learns that some people haven't left their cars in upwards of twenty years. Milo, Cheen and Martha are dropping down to the Fast Lane, but there are strange noises. Cheen tells Martha of stories about cars disappearing but Milo insists they only hear the ventilation shafts.
Brannigan and Valerie refuse to go to the Fast Lane, fearing for the safety of their kittens. The Doctor asks whether they or the Cassinis have ever seen any authorities. The Cassinis reluctantly admit they have not seen any police or ambulances in 23 years of driving. The Doctor believes that the people have been trapped in the under-city and abandoned. Making his own way toward Martha, he opens the shaft on the floor of the car and drops down to the car below. He then moves through several cars, opening the roofs with his sonic screwdriver and continuing through the floor to the car below. In this fashion he meets several characters including hippies, a Bertie Wooster-like business man and a nudist couple.
Martha's car enters the Fast Lane, but the exits are all closed. A nearby cat driver tells him to escape to the slow lanes above, but Milo does not believe in the danger until he hears the other driver's screams. Meanwhile Novice Hame reaches Brannigan's car and demands to know where the Doctor is.
The Doctor reaches the lower levels, just above the Fast Lane. He clears the fog to discover what's down there; the Macra. The Doctor explains to the car's driver that the Macra once built an empire, but have since devolved into hungry non-sentient beasts. As Martha's van races along the Fast Lane, the Macras' huge claws attempt to crush it. Reasoning that the light and motion of the vehicle attract the Macra, Martha has Milo turns off the power. It works, but they only have eight minutes of air.
Novice Hame makes it to the car that the Doctor is in. She tells him how she has repented her sins under 'his' guidance, and teleports the Doctor against his will to the upper city. She explains that everyone in the upper city, and indeed the whole surface level of New Earth died because of a virus in the Pharmacists' Bliss drug, but the under city was sealed off and Hame was protected by 'him'. The citizens in the undercity have not been betrayed and abandoned; they have been saved. Hearing a familiar telepathic voice, the Doctor runs to meet the Face of Boe. Hame says the Face has wired himself to the system to keep the lower levels functioning, but they are unable to free the people there. The Face of Boe asks the Doctor to save the people of the Motorway.
Milo's car is running out of air and, despite Milo and Cheen's doubts, Martha says the Doctor will think of something. Milo starts the power up again, giving them air but exposing them to the Macras' grasp. As the car races along, they are briefly caught by one of the claws, but break free.
The Doctor asks Hame to help him restore power, but there is not enough. The Face of Boe, in one last act of self-sacrifice, gives even more of his 'life force' to power the equipment. The Doctor pulls a lever, opening the seal at the top of the motorway. The sunlight beams in, and the Doctor broadcasts to the motorists, telling them to drive upwards and out. This clears the way for Milo's car to escape from the Macra. Meanwhile Hame cries out as the Face of Boe's glass begins to shatter.
Martha arrives at the Senate building where she sees human skeletons, and meets the dying Face of Boe, sprawled out on the ground. The Doctor urges him to live, since (as Boe says) the two of them are each the last of their kind; but the Face responds "Everything has its time". He whispers his secret - "You are not alone" - before passing away. An expression of shock and disbelief crosses the Doctor's face as Hame weeps.
Martha and the Doctor arrive back at the alleyway. The Pharmacists are gone. Martha asks what the Face meant, and whether she is why the Doctor is not alone. The Doctor shakes his head; he does not want to talk about Boe's words, but Martha refuses to move until the Doctor tells her the truth. The Doctor admits he is the last of his kind, explains about the Last Great Time War and the Daleks, and then goes on to describe Gallifrey. Far above the slums, the over-city thrives with the newly freed motorists. The sun sets orange over New New York.