The Doctor tells Martha that her one trip is over, and she can go home now... unless she wants to travel more. No reason, really, he'd just like to travel more. In fact, he'd like to take her to the future: New New New, etc., York. Where drugs are cheap, legal and socially acceptable. Where people inexplicably look like cats. Where traffic never moves. Where the Doctor also took Rose once
The Doctor even tries to make the same little jokes he made to Rose when he first took her there, but they just don't work as well when Rose isn't around to hear them. By now, Martha's figured out that she's the Doctor's "rebound", and she doesn't like it one bit. Also, the TARDIS has taken them to the undercity slums, where things aren't quite as happy as they are above the smog.
Martha gets kidnapped by a couple named Milo and Cheen so that they can have enough people in their car to get access to the elusive carpool lane. The Doctor chases after her... into the Traffic Jam From Hell.
Before he dies of extreme toxic smoke inhalation, though, he gets picked up by Cat Folk
Thomas Kinkaide Brannigan and his wife Valerie. Estimated time of arrival? Oh, another six years or so.
The Doctor, not wanting to wait that long, jumps from car to car, and tries climbing down to Martha's spot, but he can only get so far.
Meanwhile, giant evil crabs that feed off pollution
have snatched Martha's car out of the air and are hell-bent on eating her. The Doctor quickly recognizes them as the Macra and notes that they've devolved into mindless beasts over time, living in the depths of the motorway. Even if he could get there, there's hardly any way to get back.
The Doctor will not be deterred, but before he can continue he's caught by Hame, one of the cat-nurse-nuns he met during his last trip here. She transports him against his will to the upper city, where the only other remaining "person" is the Face of Boe, the oldest being in the galaxy, who's the only thing powering the motorway and keeping the rest of demi-humanity alive. It turns out that the planet's inhabitants all got wiped out by an unstoppable plague that killed everyone (including itself). And all the motorways are closed, and have been closed for years. All those cars with all their eternal fuel and food supplies are driving in eternal circles around the deadly city smog.
The quarantine placed on the planet was set to last 100 years, so it has to be released manually. The Face gives his life to open up the motorway exits and save Martha. The Doctor opens the gates and all the cars ascend into the bright upper city, with the people inside praising Jehova for saving them from the Macra.
As Face dies, he imparts his final message, as foreshadowed in "New Earth"
. The message? "You are not alone.
Martha refuses to leave until the Doctor tells her just what he is and what's going on. The Doctor sits down with her and tells his story from the beginning, starting with "there was a war"...
- Action Prologue: The episode begins with a couple's flying car on a motorway being attacked by an unseen menace.
- Adventurer Outfit: Brannigan.
- Adult Fear: This episode becomes very disturbing if you start thinking about being stuck in an inescapable traffic jam that will never end.
The Doctor: What if the traffic jam never stops? What if there's no help coming, not ever? What if there's nothing? Just the motorway, with the cars going round and round and round and round, never stopping. Forever.
- Not to mention the idea that the world could come to an end without you realizing it. Your trap is your salvation, unless some outside party decides to come help you. And barring The Doctor, there's no help coming for another 70 years.
- Aliens of London: Despite being New New York, everyone there (barring Brannigan and the news anchor) sounds very British due to the TARDIS' Translation Convention.
- Always Save the Girl:
Brannigan: This Martha... she must mean a lot to you.
The Doctor: Hardly know her. I was too busy showing off.
- American Gothic Couple: The couple in the opening who are attacked by the Macra.
- The Atoner: The cat nun who's the assistant to the Face of Boe was the survivor out of the three-named cat nuns on "New Earth".
- Big Word Shout / Say My Name: MAAAAAAAARTHAAAAAAAAAAAA!
- Call Back:
- The Macra. From a Missing Episode, no less.
- The Doctor asks for the Duke of Manhattan.
- One of the car drivers is a completely red dude — we saw another one on "New Earth".
- The City Narrows: The other side of New New York.
- Cute Kitten: Most likely the reason for an anthropomorphic cat and a demi-human woman having a litter of seemingly ordinary kittens.
- Drugs Are Bad: Both Martha and the Doctor are unamused by a street populated by drug-dealing booths that sell everything from "Happy" to "Forget" to "Honesty", and "Bliss" killed all of New Earth's population apart from New New York's undercity.
- Evolutionary Levels: The Doctor wonders if the Macra have devolved, considering they used to be intelligent but now they're just huge mindless monsters.
- Evolutionary Stasis: Despite being said in previous episodes to have changed, the humans still look human.
- First Time in the Sun: In the end, the denizens of the motorway finally ascend into the sky.
- Flat "What.": Martha's reaction to the length of time the car-jacking journey will take.
- Flying Car: In sufficient abundance to result in three-dimensional multi-lane motorways and horrifying flying traffic jams.
- "You are not alone."
- Thomas Kinkaide Brannigan: "Until Journey's End."
- Giant Enemy Crab: The Macra. They can be found at the bottom of the motorway in New New York (on New Earth). In the "fast lane", you can reach speeds of up to thirty miles per hour! (Usually taking six years to get to Brooklyn from Queens!) However, this comes with a risk: the potential of being sliced and mauled by the Macra. What's even scarier is that you only really get to see these claws above the fumes.
- Hood Hopping: The Doctor does a three-dimensional version.
- Hypocritical Humor: Brannigan refers to the Cassinis as "sisters", claiming that he's a traditional type despite being a catman married to a humanoid.
- I Ate What?: Martha is disgusted to learn that food in the cars is made from recycled waste, after taking a few bites of a cookie offered to her.
- Infant Immortality: Averted. The second car on-screen to fall victim to the Macra is a car carrying two young twins.
- Interspecies Romance: The Brannigans. She's demi-human, he's a cat-man; their kids are a litter of kittens (who can say "Mama").
- Muck Monster: The Macra.
- National Stereotypes: Irish Catman. Including that one guy who really went out of his way to look British. Bowler hat, something about manners...
- New Neo City: New New New New New New New New New New New New New New New New York.
- No Antagonist: A rare Doctor Who story with no sentient villain. Even the virus that wiped out the entire population of New Earth has long since perished, having had no-one left alive to infect and propagate itself with.
- Nobody over 50 Is Gay: Averted with the Cassinis, an elderly lesbian couple.
- One Drink Will Kill the Baby: When Martha finds out that Cheen is pregnant, she rips off Cheen's Honesty patch in disgust.
- One-Word Title
- Police Are Useless: A call to the police gets the Doctor put on hold. A call to the Cassinis reveals that there aren't police.
- Planet of Hats: All of the cars the Doctor passes through have obvious themes, be they white décor, Harajuku fashion, hippy nudism, red décor, or stylish fifties Britain.
- Selective Obliviousness: Everyone is aware on some level that they've not seen any sign from the government and/or the people on the surface for over 20 years, but it takes some serious prodding from the Doctor before they even start to acknowledge the Elephant in the Living Room.
- Shout-Out: According to Word of God, the concept of an endless traffic jam in a dystopian city is a shoutout to Mega-City One in Judge Dredd, and the man with the bowler hat is based on Max Normal, a supporting character in the comic.
- Unusually Uninteresting Sight: The people on the underground motorway are disturbingly blasé about the fact that nobody ever gets anywhere, that there's no police, and that the news doesn't do anything special. Martha needs to take a bit of time to adjust to this. This helps to make people never question what happened: the surface got wiped out by a virus.
- Villain Decay: Deliberately invoked. After a few billion years, the Macra devolved into a much less intelligent form, so instead of being invisible puppet masters (like the Silence would be later in New Who), they're just giant crabs living on car fumes.
- You Are Not Alone / There Is Another: So says the Face of Boe.