Number One gives the Captain's Log for the episode, setting the stage: an away team has visited Hetemit IX. The planet once hosted a colony of Illyrians, a humanoid species known for using genetic engineering for Bio-Augmentation. Hence the Enterprise's mission: The Federation, despite its utopian ideals, is a "No Transhumanism Allowed" civilization, and Starfleet needs to keep track of the Illyrians. This is a little difficult because the colony is abandoned, and plus an "ion storm" Negative Space Wedgie is about to hit the planet. Number One, Ensign Lance and others beam back up, while Pike hunts down Spock: the latter is in the library, reading. Transporter Chief Kyle and Chief Engineer Hemmer need to do some creative beaming to get the away team back through the ion storm, and The Captain and the Badass Bookworm end up being left behind.
Number One, the ship's Number Two, takes command while Pike is on the surface. Almost immediately, things get interesting: Ortegas spots Ens. Lance stripping his clothes off and headbutting through a light panel. He and several other landing party members are soon confined to Sickbay, where Dr. M'Benga reports identical symptoms: serious vitamin D deficiencies and an irrational need to be exposed to light. Number One suggests M'Benga take a blood sample, since she was on the landing party as well. She conspicuously doesn't mention to him that she actually experienced similar symptoms while in her quarters, shortly before her skin glowed red with Volcanic Veins. This will be important later.
Pike and Spock are, as mentioned before, trapped on the surface. Spock takes the opportunity to keep reading the logs in the library. He learns that the Illyrians were actually attempting to de-modify themselves so that they could get into the Federation, but that they disappeared soon after. Meanwhile, the ion storm causes several glowing ghost things to appear. The ghost-things smash their way into the library, despite the Starfleet officers' attempts to keep them out... but, as they do, the library window shatters under the force of the storm, and the ghost-things form a barrier around the two humans. Spock hypothesizes that they have found what became of the colonists, mentioning that they were afflicted by a condition which caused them to become addicted to light.
Back on board the ship, Number One has suddenly found herself amidst a Medical Drama. The transporters' biofilters didn't catch anything, as they are all networked together; Hemmer assures her that they can't fail — they don't blacklist pathogens, they whitelist the people using them; and besides, they're all networked together, so even if one transporter breaks, the others will step in. Number One, perhaps inspired by the location, also tries to investigate Illyrian genetic modifications in the hopes that they will give up some secrets. La'an, coming in, joins in Number One's griping: As a descendent of Khan Noonien Singh, the Genius Bruiser Evil Overlord who caused the Eugenics Wars (AKA "World War III," at least according to Pike in the pilot episode), she understands precisely why the Federation's "No Transhumanism Allowed" ban exists, even if she's frustrated with how much grief it caused her as a child despite the fact that La'an isn't an "Augment" herself. However, Number One's other hope — that La'an, Chief of Security, can help her round up any symptomatic officers — is squashed when La'an herself comes down with the condition on the spot. Even weirder, Cadet Uhura wakes up with her roommates having the condition... but lacking it herself. She mentions that she keeps her bunk pitch-black to get to sleep, leading Number One to theorize that the condition is transmitted by light. Number One orders all the lights turned off, and orders the entire crew to retreat to lockdown.
Hemmer comes to visit Dr. M'Benga in Sickbay. He has found an anomaly with the emergency medical transporter, which seems to be using excess power. M'Benga is clearly ruffled at the intrusion, and even resorts to turning the lights off — claiming that it was due to Hemmer's meddling — to get the Chief Engineer to leave. It's not for long, of course: Hemmer soon contracts the condition, and Number One submits him to Sickbay shortly after stunning him with a phaser because he was attempting to beam lava up from the planet. M'Benga, Chapel and Number One realize that the three of them are, more or less, the only ones still standing. Number One asks about the blood sample she submitted, and finally admits why she submitted it: she, the human-looking Una Chin-Riley, is actually an Illyrian, and has Ideal Illness Immunity. The red glow she experienced was her body instantly neutralizing the disease. Unfortunately, this is actually Less Than Ideal Illness Immunity: because her body instantly neutralized the disease, there were no antibodies left for Chapel to find. While the two doctors uphold the Hippocratic Oath, having absolutely no problems exploiting Una's unique physiology if it'll help the situation, M'Benga needs to be sedated as he's come down with the condition... and Una finds Chapel on the floor, and La'an gone, and the ship's computer announcing the Exact Time to Failure on the ship's warp core containment field. La'an wants light, and an uncontrolled deuterium-antimatter explosion is just the thing to get it. Even better, it would let her take revenge on Una — the friend who lied to her every day about being an "Augment." Una knocks La'an out, but not before the containment field goes down, flooding Engineering with radiation. Her skin glows red.
In Sickbay, Una brings Dr. M'Benga out of sedation. Her Healing Factor saved both her and La'an, and she was able to rush back to Sickbay quickly enough that Chapel could isolate the antibodies and synthesize a cure. She then goes to apologize to La'an for lying. She admits that she'd gotten so used to hiding who she was that she did it even with La'an, one of the only people who understands what it's like to receive Fantastic Racism. She then reports to Capt. Pike and turns in her badge, knowing he must prosecute her for lying to get into Starfleet; but Pike just rolls his eyes: reading those library books with Spock has made it clear to him that Illyrians are severely misunderstood, and Una's exemplary actions have only underlined this. Finally, Una visits with Dr. M'Benga, having traced the problem down to the biofilters in the emergency medical transporter, which M'Benga insisted not receive upgrades when the Enterprise was in Spacedock. M'Benga admits that he is using the pattern buffer as a way to store his daughter, the Littlest Cancer Patient, in suspended animation, and that he was willing to risk every life on the ship to save her. He asks only a moment to say goodbye to her before being turned over to Starfleet for justice... but Una simply offers to run a dedicated power source to the pattern buffer, which would prevent the problem from happening again. As the episode closes, M'Benga raises the privacy screens on Sickbay and then materializes Rukiya to read her a story.
Tropes:
- Addled Addict: Extreme Vitamin D deficiency causes victims of the light disease to seek out the brightest sources of light they can find, heedless of their own safety. This escalates from some cadets turning up the light to scalding levels, to Hemmer trying to beam up a piece of the planet's mantle, and finally to La'an engineering a warp core breach just to satisfy their cravings. Some Illyrians are noted to have run into an ion storm to be obliterated by the lightning.
- Berserk Button: La'an was bullied as a child for her distant connection to the Augments who were responsible for the Eugenics Wars — so she is pissed off to learn that Una is really part of an entire species of Augments.
- Bizarre Alien Biology:
- The light disease propagates over light waves from infected victims.
- Illyrians develop weird glowing Volcanic Veins when their immune systems are in overdrive, serving as a Glamour Failure for human-passing ones like Una.
- Call-Forward: M'Benga's technique of keeping his daughter in Suspended Animation in the medical transporter's pattern buffer is a clear parallel to how Scotty later saved his own life and attempted to save a crewmember, after the crash of the transport ship Jenolan late in the 23rd century, by using this method.
- Captain's Log: The episode opens with Una delivering the First Officer's log, explaining that they're investigating an Illyrian colony that was abandoned due to frequent ion storms. She also ends the episode with one about being an Illyrian, which she deletes."First officer's log, stardate 1224.3. The Enterprise has arrived at Hetemit IX, the site of an abandoned Illyrian colony. Illyrians are a humanoid species known for modifying their genes to enhance their capabilities and levels of function. However, because genetic modification is forbidden in the Federation, they have always been outcasts. Our presence here is part of a standing mission to discover what happened to them. Unfortunately, research time on the surface is limited, as the planet is regularly swept by ion storms, one of which is fast approaching."
"First officer's personal log. The lights are back on, but that doesn't mean we see clearly. People are always hiding things. Dr. M'Benga stopped hiding today, just a little. And for once, I did too. I told Captain Pike the truth about myself, and he defended me. Told me I was exemplary, that he would fight for me. So why do I feel terrible? What if I hadn't saved all those lives? Would the captain feel the same? What would he do if I wasn't a hero, one of the 'good ones'? When will it be enough to just... be an Illyrian?" [Beat] "Computer... delete log entry."- Which brings to mind another incident of a Starfleet officer deleting a log immediately after recording it.
- Comically Missing the Point: When Una attempts to stop Hemmer beaming aboard a piece of planet core, she tells him it's 1,000 degrees and will kill him. He corrects her that it's more like 10,000 degrees (which would melt at least half the Enterprise), and then continues to play with the console.
- Curb-Stomp Battle: La'an is completely outmatched against Una, and the only reason the fight lasts as long as it does is because Una is more concerned with reactivating the warp core containment field than making sure La'an stays down. Once it's clear La'an won't see reason and won't stop being a problem, Una lays her out with one punch.
- Dark and Troubled Past: In addition to her previously-established past on a Gorn nursery, La'an reveals that she was bullied for her relation to Khan, being derogatorily called an "Augment" by other children.
- Death by Irony: The Illyrians modified themselves to instantly eradicate any disease the moment they came in contact with it. This colony, upon removing that modification, were killed by a strange disease.
- Designated Girl Fight: Una and La'an slug it out when the latter attempts to drop the warp core containment field, partially motivated by La'an being furious over Una's lies about being an Illyrian. Una has the clear advantage in the fight and isn't taking it seriously, eventually slugging La'an unconscious.
- Energy Beings: The ion storm is full of wraith-like energy beings. Spock theorizes that they're a result of crazed colonists running into the ion storm and being vaporized, with an imprint being left behind.
- Fantastic Racism: The stigmatism behind genetic augmentation extends towards those born already modified. As M’Benga ruefully tells Una, they traded one prejudice for another.
- Fantastic Slur: "Augment" was used in this manner against La'an for being related to an actual Augment, Khan, even though La'an herself isn't one.
- Foreshadowing:
- Una experiences the symptoms of the light disease, only for her veins to glow and the symptoms to immediately stop. She then hides that any of this happened when reporting to Sickbay, showing that what's happening to her is distinct from the rest of the crew. She also slings Hemmer over her shoulder like a duffel bag with no obvious difficulty, which Chapel takes note of, when a fully-grown humanoid shouldn't be an easy lift for anyone short of a bodybuilder.
- Una's glow happens to vaguely resemble the Energy Beings that Pike and Spock observe, as they're also (or were also) Illyrians.
- M'Benga is oddly defensive of the medical transporter when Hemmer comes to examine it, and covertly dims the lights when he messes with it to make him leave. This shows there must be something about it that he really doesn't want tampered with, and is trying to hide that fact.
- Spock points out the energy creatures only began appearing after the Illyrians began to fall to the disease, and that there's no record of the creatures harming the colonists - foreshadowing they are trying to save them and that they are the Illyrians.
- Help Mistaken for Attack: Pike and Spock assume that the Energy Beings trying to bash the door down are a threat. When they succeed, however, they turn themselves into Deflector Shields to protect our heroes from the ion storm.
- Human Aliens: Sorta. The Illyrians as introduced on Star Trek: Enterprise are bog-standard Rubber-Forehead Aliens, but Una looks human enough to pass as one and have a long career in Starfleet without anyone figuring out the ruse. This may be a result of whatever genetic engineering was done to her. A file on Illyrian genetic modifications shows images of children with various different appearances.
- Infectious Insanity: The light addiction is contagious and gradually most members of the crew succumb.
- Light Is Not Good: The disease causes victims to become obsessed with light to a suicidal level, and it travels on infected light waves.
- Littlest Cancer Patient: Rukiya has cygnokemia and, at the time of diagnosis, had 12 weeks to live.
- Meaningful Background Event: While Una and M'Benga argue about whether or not her Illyrian blood can help treat the infection, La'an (who's supposed to be sedated) sits up in her bed. Moments later, she's missing from Sickbay and an alarm sounds in Engineering.
- Mythology Gag:
- At the end of the episode, Una reveals some hard truths about herself and her fears in her log before ordering the computer to delete the log, similar to what Sisko would do in the iconic Star Trek: Deep Space Nine episode "In the Pale Moonlight".
- Number One's Illyrian background was previously established in the novel Vulcan's Glory by D.C. Fontana, albeit with a different history for her and no known prejudice against Illyrians in the Federation.
- Non-Malicious Monster: The Energy Beings are just trying to protect Pike and Spock, even if it means bashing down the door to get to them.
- No Transhumanism Allowed: The Illyrians practiced genetic modification freely, which kept them out of the Federation due to the long-standing stigma against it there. The Illyrians of this specific colony were trying to reverse their modifications to gain Federation membership. The crux of this episode is a critique on this stance, about how the Federation's strict prohibition stems from a traumatic reaction to historical mass-murdering madmen who were Augments, and how the Illyrians' philosophy on it is as a harmony with nature, especially when colonizing other planets, may be a more healthy take on the matter. Number One posits that it's a far less drastic measure to adapt colonists to a colony world through genetic engineering than to upend the planet's existing environment with terraforming. It also examines how prejudice and ostracism still rears its ugly head in the supposedly enlightened Federation when it comes to people with genetic engineering, with Dr. M'Benga's laments and Singh's childhood torment.
- Outliving One's Offspring: It turns out that Dr. M'Benga is desperately trying to avert this with his cancer-stricken daughter, stashing her in a kind of Suspended Animation the Emergency Medical Transporter's pattern buffer to prolong her mere weeks of prognosis until he can potentially find a discovery leading to a cure out on the Final Frontier.
- Over-the-Shoulder Carry: Una slings Hemmer over her shoulder to carry him to Sickbay. The fact that she can lift a full-grown humanoid so easily serves as foreshadowing of her true nature.
- Punch Catch: Una catches a fist from La'an in the beginning of their throw-down in Main Engineering.
- The Reveal:
- Una is actually an Illyrian.
- M'Benga has his daughter stored in the pattern buffer of the emergency medical transporter, keeping her in suspended animation so she won't be killed by an incurable disease. As long as he materializes her every so often, he can extend her life until a cure can be found.
- Screw the Rules, I'm Doing What's Right!: Pike refuses to allow Una to resign for lying about being an Illyrian, as her actions prove the Federation was wrong to stigmatize them without seeking to understand them.
- Sequel Episode: A spiritual one to TOS's "The Naked Time" and TNG's "The Naked Now" note . All three involve an infection sneaking onto the Enterprise and affecting pretty much the entire crew. While the earlier (or rather later) polywater infections removed all inhibitions, the "light virus" is so dominating that it causes the crew to disregard any sense of safety, such as headbutting a light fixture, getting an extra crispy tan, or even beaming a piece of a planet core onto the ship.
- Unwitting Instigator of Doom: M'Benga refusing to update the medical transporters so his daughter could continue to survive in the pattern buffer is what causes the epidemic on the ship.
- Volcanic Veins: Una exhibits these after demonstrating symptoms of the light disease, despite otherwise appearing asymptomatic. She later reveals it to be a feature of her biology, as she's secretly Illyrian, a visual indicator of her immune system reacting to disease.
- You Are a Credit to Your Race: Discussed by Una in her last log entry of the episode, before deleting it. She wonders if her co-workers would be so accepting if she were just an Illyrian and not one who'd been exceptional and heroic.
- Zombie Infectee: Una appears to be this at first, but is later revealed to have resisted the infection thanks to her advanced immune system.
