Written by Helen Raynor.
Paging the Doctor! When Martha gave the Doctor her old phone, this is the kind of situation she had in mind.
Since he left, remarkable strides have been made in environmental engineering: in particular ATMOS, a gizmo installed in half the cars on Earth which neutralizes exhaust, with only the tiny side detail of being completely evil and a front for alien murders. ATMOS is the creation of a teenage genius by the name of Luke Rattigan, who is secretly working for the Sontarans, a warrior race of militaristic short guys who look a bit like potatoes. (Though the Doctor would like to remind you that to a Sontaran, you look like a shaved pink weasel-thing.)
Martha and Donna are introduced and, to the Doctor's great relief, get on really well. Martha's now a proper doctor, and with UNIT. The Doctor's a little bit uncomfortable with how well she fits into a military organisation. She retorts that he's the one who got her the job in the first place. He wisely doesn't respond to that.
The Doctor teams up with UNIT, but he doesn't like the way things have changed since the old days, and the reunion is an uneasy one. The Brigadier (now knighted) is a few continents away and unable to help out. Also, Martha is kidnapped by the Sontarans, and they create an evil clone of her.
Meanwhile, Donna goes back home to get another earful from her mum, and to see Wilfred, her dear old grandad, again. The Doctor turns up to fetch her (and meets a delighted Wilfred and a highly apprehensive mum), just in time for all the ATMOS-equipped cars in the world to begin emitting clouds of poison gas! How can the Doctor stop an alien attack that's occurring in 400 million places at once?
- Absence of Evidence: Donna's days as an office worker come in handy as they allow her to notice something off about the factory's workers:Donna: The first thing I noticed is an empty file.
The Doctor: Why, what's inside it? Or, what's not inside it?
Donna: Sick days. There aren't any. Hundreds of people working here and no one's sick. Not one hangover, man flu, sneaky little shopping trip, nothing. Not ever! They don't get ill.
- Affably Evil: General Staal is as cordial as a Sontaran ever gets towards the two soldiers he meets, up until one of them starts with the height jokes.
- And Starring: Freema Agyeman is credited with an "And".
- Arc Words: Another reference to the Medusa Cascade.
- Artistic Licence Gun Safety: The Sontarans use cordolane signals that render ordinary firearms useless, and this is said to work by expanding the copper jackets of the bullets so that they can't leave the barrel. In reality, such a malfunction often causes the affected weapon to explode; the stuck bullet denies the burnt gunpowder gases any safe exit, so they exit unsafely instead by bursting the chamber or barrel. Fortunately for the UNIT soldiers, in the episode it only results in the same click you'd get from a dry fire.
- Badass Bureaucrat: Donna finds the problem with the ATMOS workforce using her office skills to find the empty folder that's meant to contain the paperwork for staff sickdays.
- Bait-and-Switch: Donna approaches the Doctor and asks for a ride home. Seeing the solemn look on her face he launches into a speech about all the sights he wanted to take her to see...and then realises she just wants to check on her family and isn't leaving him permanently.
- Barefoot Captives: A justified example - the Sontarans need Martha's clothes to allow her clone to blend in. She is given something resembling a hospital gown for modesty reasons, but is left barefoot.
- Berserk Button: Don't say the Sontarans have a weakness, even if they actually do.
- Blue-and-Orange Morality: The Tenth Doctor's notorious loathing of guns leaks into the people that carry them. He is snotty towards Colonel Mace, a Reasonable Authority Figure, and Ross, a Nice Guy grunt, because they carry guns. He says that people who carry guns are usually bad guys, but Martha gives him an earful for this. The Brigadier, who the Doctor later wishes was involved in the situation, is the exception to this rule though the Doctor felt this way towards the Brigadier, at first.
- Blunt Metaphors Trauma: Rattigan remarks that something is "cool", and Staal remarks "Is the temperature significant?"
- Boring, but Practical: Donna's credentials in investigating ATMOS pale in comparison to UNIT's military might and the Doctor's genius, but she's the only one who's able to actually find a lead. How? She reviews the company's paperwork and immediately discovers an empty file that's supposed to list sick days, revealing that non-humans (specifically, clones) are involved.
- The Brigadier: Colonel Mace is a leading figure in UNIT, the military organization in charge of Homeworld Security. He's a pretty nice guy. The trope namer himself doesn't appear he's stuck in Peru.
- Broken Record: The factory worker Martha interviews only answers questions with "I am here to work".
- The Bus Came Back: Martha returns for a few episodes.
- Capture and Replicate: The Sontarans make a clone of Martha in order to infiltrate UNIT.
- Chekhov's Gun: Both the racketball in Luke's office and the rubber mallet used to whack the TARDIS console are used again to incapacitate Sontarans.
- Cliffhanger: Wilf is trapped in the car as the ATMOS devices are activated...
- Comically Missing the Point: Rattigan calls the Doctor "smarter than the average UNIT grunts". The Doctor gets upset and insists that he not call Ross, his escort, a grunt.
- Continuity Nod:
- To "Voyage of the Damned" (when Donna's grandfather met the Doctor) and "The Runaway Bride" (when Donna's mother met the Doctor).
- And "Dalek" (the "In-tru-da window" pun made by Henry van Statten).
- Donna's mother complains about Donna disappearing for days.
- The Sontarans mention the Time War, and how the Doctor fought in it. They're upset because they weren't allowed to take part.
- Covered in Gunge: A creature in a pool of green slime.
- Cursed with Awesome: The Sontarans' armour has only one weak point, in the back of their necks. For the Sontarans, retreat is not only dishonourable, but impractical.
- Defeating the Undefeatable: Staal introduces himself as "Staal the Undefeated". The Doctor points out the lack of foresight, pointing out that if he is defeated, he'll have to be called "Staal the Not-Quite-So-Undefeated-Anymore-But-Never-Mind".
- Ditto Aliens: Staal and Skorr, being clones, have only minor differences. Luke Rattigan's reaction when Skorr removes his helmet says everything:Luke Rattigan: How... do you tell each other apart?
General Staal: We say the same of humans.
- Does Not Like Guns: The Doctor is particularly sharp to Colonel Mace and tells him to back off because he's carrying a gun, which the Doctor doesn't want anywhere near him.
- The Dragon: Commander Skorr "the Bloodbringer" is the field commander.
- The Easy Way or the Hard Way: The soon-to-be-brainwashed UNIT soldiers tell the already brainwashed factory workers of their options.
- Every Car Is a Pinto: Subverted when the ATMOS in the Land Rover suffers from the Logic Bomb: the Doctor and Ross Jenkins run for cover... then the sat nav system fizzles and sparks a little bit.The Doctor: [disappointed] Oh, is that it?
- Exact Words: The ATMOS in the UNIT jeep was programmed to do precisely the opposite of what the Doctor tells it. So he tells it to drive into the river.
- Failed Attempt at Drama: Donna says she's going home. The Doctor gives her the big speech about everything he wanted to show her, how she's saved his life, how he was so very grateful for her company and... "you're just popping home for a visit, aren't you?" Also a stellar example of The Day the Music Lied.Donna: You dumbo. You great, big, outer space dunce.
- Fate Worse than Death: A Sontaran would rather just shoot a person than brainwash them, because "Death has more honour". That doesn't stop them, though.
- The ATMOS satnav repeatedly saying "Turn Left".
- There's also the cloned copy of a person animated by the still-living person's memories.
- Fun with Acronyms: Both ATMOS and UNIT use the "using letters from within the words" method.
- UNIT now stands for UNified Intelligence Taskforce instead of United Nations Intelligence Taskforce. It was enforced for them they didn't before, but then the UN started being much more sensitive about its name being used.
- Taken to its logical conclusion with ATMOS, which stands for "Atmospheric Omissions System". The final S has to come from System, or Rattigan's whining makes no sense. One would think "omissions" is a misspelling of "emissions", but it's actually a pun: the system takes the dangerous chemicals out of the car's emissions; it's an emission omission system. That's just the kind of joke somebody like Rattigan would think was clever.
- Godwin's Law: Ross the UNIT soldier compares Rattigan's followers to the Hitler Youth. It has dawn excercise and special diets and stuff.
- Grammar Nazi:
- The Doctor:Luke: If only that was possible.
The Doctor: If only that were possible. [glasses pull] Conditional clause.
- Later...Luke: You can't say "ATMOS System" 'cos it stands for Atmospheric Omission System. So you're saying, "Atmospheric Omission System System". Do you see, Mr. Conditional Clause?
- The Doctor:
- Guns Are Worthless: The Sontarans' Applied Phlebotinum prevents guns from being fired in their presence. Technobabble explains that it's because of the bullets' copper jackets.
- Helmets Are Hardly Heroic: Justified In-Universe as it's a sign of bravery for Sontarans to face their enemy unprotected. After seeing his commander has taken off his helmet, his Number Two requests permission to do likewise.
- Hollywood Spelling: "If you're gonna go to print, spell my name right. Rattigan, with two ts."
- Hypocrite: Sontarans are a group of Proud Warrior Race Guys who've never run from a battle, but cripple the UNIT soldiers so they can't fight back.
- I Can't Feel My Legs!: Staal's Boom Stick shoots a paralyzing beam.
- Idiot Ball:
- At the start of the episode Jo Nakashima is protesting at how dangerous cars with ATMOS are, and then proceeds to get into one.
- Martha walks into a secluded area with a couple of grunts that only ask for her security clearance before escorting her away. This is after she suspects hypnotism and is going to talk with Colonel Mace. (Admittedly, the grunts in question claim they were sent to find her by the Colonel...)
- Insufferable Genius: Luke Rattigan doesn't like it when someone out-geniuses him. See Grammar Nazi for just one example of it.
- Insult Misfire: Don't call Ross a grunt.
- It Seemed Trivial: UNIT phones ahead to tell Luke that the Doctor is coming to see him. Luke hears this as "the doctor", and thus when General Staal asks him who the Doctor is, he responds with "He didn't give his name." Later, after the Doctor and Ross have left in a hurry, and the Sontarans are trying to find them:Luke: That doctor, he was in a UNIT jeep.
Staal: ... You said you didn't know his name.
Luke: I don't, he just said "doctor".
- Just One Second Out of Sync: The ATMOS has a "temporal pocket" containing the gas emitter.
- Lampshade Hanging: The Doctor himself isn't sure if he worked for UNIT in the 70s or the 80s.
- Logic Bomb: Used by the Doctor to escape Murder by Remote Control Vehicle. The AI has been programmed to kill the Doctor and to disobey any order the Doctor gave it, so the Doctor orders it to do what it's actively trying to do to him, which is kill him.
- May Contain Evil: The ATMOS reduces emissions and works as a sat-nav system. Also, it can completely take over your car and is designed to release a poisonous gas.
- Meaningful Name: The character who betrays humanity to the Sontarans is called Rattigan.
- The Missus and the Ex: Subverted; the Doctor attempts to head this off, only for Donna and Martha to jump straight to making fun of him. "Oh, I'd rather you were fighting."
- Murder by Remote Control Vehicle: The episode starts with a journalist being killed by her own car when its emissions reduction system (part of a planet-conquering ploy by the eponymous Sontarans) takes over. The Doctor is then himself trapped in a car controlled by a murderous AI, but escapes by using a Logic Bomb. (The AI has been programmed to kill the Doctor and to disobey any order the Doctor gives it, so the Doctor orders it to kill him.)
- Names to Run Away from Really Fast: Skorr the Bloodbringer.
- Nerd in Evil's Helmet: Luke Rattigan clearly wants to be some kind of Bond villain, and is just as clearly trying way too hard.
- No One Could Survive That!: Largely averted. The Sontarans initially think the Doctor is dead, but when they get proof that he's not, they accept it without question. Of course, they know the Doctor, so obviously they'd know how hard it is to kill him.
- Not That Kind of Doctor: Luke Rattigan, having never heard of the Doctor before in his life, misinterprets the phone call from UNIT informing him of his visitor as that "the doctor" is coming to see him. So, when General Staal arrives in Luke's study, and the Doctor taunts him repeatedly:Staal: Who is this?
Luke: He didn't give his name.
- OOC Is Serious Business: The Doctor is baffled that the Sontarans are using trickery and subterfuge instead of a direct attack. As it turns out, the Sontarans actually want to use the planet for clone production instead of straight-up conquering it.
- Proud Warrior Race Guy: All the Sontarans talk about the "delight of battle" and how a "good soldier" joins the fray personally. The Doctor points out that hiding and stopping bullets are very unlike them. "A Sontaran should face bullets with dignity, shame on you!"
- Pun: "We have an intruder." The Doctor responds with: "How did he get in? In-tru-da window?", referring back to "Dalek".
- Red Baron: General Staal the Undefeated and Commander Skorr the Bloodbringer. The Doctor mocks the former thoroughly.
- Red Shirt: Red Berets, in this case; the UNIT soldiers are easily-killed foot soldiers for the good guys, due to the Sontarans cheating with technobabble that disables the standard copper-jacketed bullets.
- Scheherezade Gambit: On meeting Staal, the Doctor immediately reveals he knows what a Sontaran is, discouraging Staal from just killing him on the spot.
- Sherlock Scan: Donna takes a quick look through the ATMOS offices and finds an empty folder that the rest of UNIT completely overlooked.
- Shoulders-Up Nudity: Martha's clone, upon first emerging from the clone vat covered in green goo.
- Spoiled Brat: The Doctor's opinion of Rattigan.The Doctor: It's been a long time since someone said "no" to you, isn't it?
- Spoiler Title: The episode is scripted, shot and edited in such a way as to keep the aliens unseen until there is a big reveal that they are Sontarans. Too bad the title gives that away.
- Strange Minds Think Alike: The Doctor comes up with the same "In-tru-da window" pun that Henry van Statten used back in "Dalek" which he was not present to hear.
- Stuff Blowing Up: The Doctor's disappointed when Every Car Is a Pinto doesn't happen.
- Sudden Name Change: As of this episode, UNIT is Retconned to stand for "Unified Intelligence Taskforce" instead of "United Nations Intelligence Taskforce", after the real UN discovered a Viral Marketing UNIT website for Series 1 and requested their name not be used on the show again.
- Take That!: To The '80s in one way or another.note The Doctor: Getting a bit too close to the 1980s.
Donna: What am I gonna do, put a dent in 'em?
The Doctor: Well, someone did.
- Teaser-Only Character: Reporter Jo Nakashima, who's murdered by having her car driven into the water after confronting Luke Rattigan about ATMOS being dangerous.
- Teen Genius: Luke Rattigan is a teenager with an IQ "rated at 174."
- Teens Are Monsters: Rattigan is also a smug supervillain-wannabe who thinks helping the Sontarans kill dozens of people is cool. He's willing to sell out his entire species because he didn't fit in growing up.
- Tempting Fate: When Staal confronts Privates Harris and Grey, Harris mockingly asks him if he's going to bite their ankles. He then disables them by shocking them at the ankles.
- Trapped in a Sinking Car: Jo Nakashima is murdered when her car is forced to drive into the river. Later, it nearly happens to the Doctor and Ross, but the Doctor is able to Logic Bomb the ATMOS before that can happen.
- What the Hell, Hero?: Martha, who's grown to know and like Colonel Mace, calls out the Doctor for his attitude towards Mace.
- What the Hell Is That Accent?: More than one American viewer was surprised to learn that Luke Rattigan was supposed to be American.
- Where's the Kaboom?: After the UNIT jeep fails to explode at all. "Is that it?"