The Enterprise crew are talking about what places they'd like to visit, and when Trip mentions an M-class planet with five hundred million live signs on it, Archer excitedly orders a course there. They scan the planet and determine that it's home to a pre-industrial humanoid species called the Akaali, who speak several languages. T'Pol tells the crew that Vulcans usually wait until a species is warp-capable before initiating first contact, but Archer decides to check the planet out now, so Phlox gives him, T'Pol, Trip, and Hoshi plastic surgery to make them look like Akali. Meanwhile, the scans have also detected strange neutrino emissions which could mean someone else is on the planet with an antimatter reactor.
T'Pol and Hoshi walk through the streets and observe that several Akaali have lesions, while Archer and Trip find out where the neutrino emissions are coming from— a curio shop. They break into it that night and find a door protected by a force field and an Akaali woman who thinks they're in league with the shop's owner and have caused a disease among her people, since the disease started soon after the shopkeeper arrived. T'Pol appears and stuns the Akaali woman, then Hoshi finds out that her name is Riann.
The next morning, Riann wakes up to see Archer there, who claims she passed out. She doesn't believe him and asks if he's working for Garos. Archer says that he isn't working for anybody and goes to leave, but Riann asks him to explain himself. He claims he's an investigator and wants to know more about the disease, and introduces himself as "Jon".
Back in the shuttlepod, the away team talks to Malcolm, who reveals that the energy field is strong enough to withstand a torpedo barrage. Archer reveals that Riann mentioned a disease, which Hoshi wonders if it's the cause of the lesions she saw on the citizens. Trip suggests taking someone to the ship so that Phlox can examine them, but T'Pol points out that this might be seen as kidnapping, so she suggests talking to the shopkeeper.
They go to do so and scan him, determining that he's not Akaali, but then he scans them back and finds out that they aren't either. They ask each other who they are and where they're from, and it turns out that the shopkeeper is a Malurian named Garos. He explains that he moved onto the planet during a survey mission, he does indeed have an antimatter reactor but it's only to make food and clothes with, and that he's aware Riann thinks he caused the disease but sees it as her just blaming the newcomer. He asks them to leave, and they do.
Archer and T'Pol later go to Riann's apothecary to learn more about the illness. T'Pol scans Riann's equipment, while Riann explains that she learnt about the disease eighteen months ago but still doesn't know what caused it, and she knows that Garos leaves crates intended for places outside the city but doesn't know how they arrive. T'Pol finds sufficient information, so Archer sends her back to Enteprise, where Phlox analyses the samples and finds that the "disease" is actually caused by an industrial lubricant which leaked into the water supply.
Archer and Riann spy on the shop (and at one point, his universal translator glitches out so he kisses her to avoid arousing suspicion) and then follow a man who's taking crates from it. They see a Malurian shuttle take the crates onboard with a tractor beam, then one Malurian sees them and fires at them. Riann takes a device from the Malurian and finds out that he's an alien, then the two return to the city and use the device to find the reactor.
Archer then hails Enteprise, having discovered that the Malurians were using the reactor to gather an isotope of veridium, which T'Pol adds was probably used to make explosives. Archer decides to take the operation down, deciding to do so using a dampening field and the transporter, since blowing it up would be too risky. He accidentally sets off an alarm, which shuts the doors and alerts Garos, who fires a warning shot at Enterprise and claims Archer is dead.
Garos tells Archer and Riann to leave, but instead, Archer arms Riann with a phase-pistol, disables the dampening field, and then they leave. Garos keeps firing at Enterprise, while T'Pol plans to beam the reactor into space and then explode it. They do so, while Archer, Riann, and the Malurians fight, with Archer and Riann winning. Garos is informed that the reactor is destroyed, so he leaves. Archer then gives Riann medication for the sickness and tells her to keep what happened to herself, then she kisses him.
Tropes in this episode include:
- Alien Non-Interference Clause: T'Pol introduces her shipmates to the idea of not revealing themselves to pre-warp cultures.
- Artistic License – Space: Okay, how exactly would an acoustic relay work in space?
- Bad Liar: Archer sucks at lying to Riann. She calls him out each time.
- Brick Joke: When Archer kisses Riann for real, she jokingly asks if his Universal Translator is on the blink again.
- Call-Back: Archer makes a quip about aliens landing in cornfields. Just like Klaang, Johnny-boy?
- Call-Forward: The Malurians were later mentioned to have been wiped out in TOS's "The Changeling."
- Exact Words: T'Pol points out that she ordered them to prepare to leave orbit, rather than leave orbit.
- Forced Kiss: Archer kisses Riann when his translator conks out to cover while he restarts it.
- Hoist by Their Own Petard: Enterprise disables the Malurian ship by beaming their mining reactor in front of them and detonating it.
- Interspecies Romance: The episode ends with an Akaali (Riann) kissing a human (Archer).
- Lizard Folk: Archer peels away part of a Malurian's prosthetics to reveal that they're reptilian.
- A Million Is a Statistic: Garos doesn't care about a few thousand Akaali deaths.
- Mistaken for Disease: The Akaali believe they're suffering from an epidemic when they break out in lesions, but it turns out to actually be from poisoned water instead.
- No OSHA Compliance: What caused the sickness in the first place—a highly toxic chemical leaked into the water supply from the drills Garos uses to mine for veridium.
- No-Sell: Enterprise's torpedoes don't work against the Malurian's Deflector Shields, so they use the above tactic with the reactor.
- The Scapegoat: Garos claims that Riann is blaming him for the disease since she and her people don't know any better—until it turns out that she's right.
- Thinking Out Loud: Riann admits that she talks to herself when she's thinking. Archer compares it to him talking to Porthos.
- Title Drop: Provided by Trip during The Teaser:"If our scans are right, it looks like there's a whole civilization down there."
- The Triple: T'Pol shows Archer three objects of interest—a supernova remnant, a trinary neutron star cluster, and a planet with 500 million inhabitants. Naturally, our heroes get the most excited over the last one.Archer: You might've put that at the top of the list.
