Original air date: May 9, 1988
However, a priority call to Picard interrupts the mission, as it's Picard's old friend, Captain Walker Keel, on the line. He demands for the ship to detour to an abandoned mining planet for a secret meeting. Picard is confused but curious, and humors him. Upon arriving at the planet and beaming down, Picard is confronted by not just Keel, but two other captains, who try to Bluff the Impostor to make sure Picard is really Picard before telling them of their concerns of a subversion in the Federation. The evidence is both vague and disturbing: mysterious disappearances and deaths in the ranks, bizarre orders and personnel shuffles, among other things. Picard doesn't buy it, but agrees to keep his eyes open for anything unusual that would corroborate their stories, assigning Data to look over Starfleet's recent activities upon returning to the ship as a precaution before heading back on course to Pacifica.
Unfortunately, the conspiracy decided to make its presence known shortly thereafter; the Enterprise comes across the destroyed wreckage of Keel's ship, and through his research, Data is able to confirm many of the odd occurrences Picard was told of, leading everyone to assume the worst: secret invasion. Picard decides to head to Starfleet Headquarters to figure out just what the hell is going on. Once there, Picard and Riker meet with a trio of admirals, all of whom seem to be acting very strangely. Things get weirder when we learn that one of them is Admiral Quinn, who, in a previous episode ("Coming of Age"), started the rumors of the conspiracy, but now insists he was only speaking metaphorically about acquiring new members of the Federation. While Riker is still not convinced, Picard is, and orders him to keep an eye on this admiral while he goes on a tour of the Enterprise.
Once on board, Quinn introduces Riker to a brain slug (no, not those ones), batting him around like a rag doll when he refuses to become one with the thing. When Worf and Geordi fail to stop him, Quinn is eventually subdued by Dr. Crusher, and an investigation reveals a similar brain slug within him. Apparently, these are the things that are trying to subvert the Federation, and as Picard soon learns, they've made their way into the highest levels of Starfleet. Fortunately, Riker recovers enough from his beating to pull off a successful fake-out to rescue Picard from assimilation, and together, they face off against the mother alien, possessing Quinn's second-in-command, Commander Dexter Remmick, who defiantly insists they only wanted "peaceful coexistence". The episode ends on a Red Herring Twist, with a homing signal being sent out to the Delta Quadrant. The End... Or Is It?
This episode was originally meant to be the prelude to the Borg, but was ultimately left hanging as an cliffhanger, never to be followed up upon. Except, that is, in the Star Trek Expanded Universe, where the story got several contradictory resolutions. In the Star Trek Novel Verse the parasites are revealed to be mad, genetically engineered Trill symbionts that the Trill don't like to talk about, essentially the Trills' cultural equivalent to Romulans. In Star Trek Online, they're instead Solanae-engineered infiltrators made for the Iconians to infiltrate the Vaadwaur.
This episode contains examples of:
- Aborted Arc: The series never followed up on the final cliffhanger in this episode—at least not straight: The Borg were originally going to be the follow-up to this episode and be an insect-like race, but that was too expensive.
- Absentee Actor: Wesley again does not appear.
- Alien Lunch: The slug-controlled people eat live maggots.
- Artistic License Biology: The parasites have control of their hosts adrenal glands, which gives them superior strength and durability. In reality, even a stiff shot of adrenaline isn't going to let an old man deliver high-kicks, beat up three fit young men, or resist a stunning effect that would instantly render a normal human unconscious.
- Batman Gambit: The controlled Starfleet officers reveal they knew about the secret meeting (as one of them was there). They orchestrated events so that Picard would head to Earth and be in a position to be overtaken.
- Beware the Nice Ones: Doctor Crusher just happens to have a phaser on hand to deal with Admiral Quinn, who has already taken down Riker, Geordi, and Worf.
- Big Damn Heroes:
- Dr. Crusher comes along just in time.
- It doesn't look like it at the time, but Riker appearing at the dinner.
- Blatant Lies: "You don't understand. We mean you no harm. We seek peaceful co-existence!"
- Body Horror: The mother-alien hiding underneath Remmick. And before that, we "get" to see Remmick's head explode. This is not your average TNG episode.
- Brains and Brawn: How the possessed Scott describes the "relationship" between the slugs and those they possess."It's a perfect match. We're the brains, you're the brawn."
- Brainwashed and Crazy: Everyone affected by the slugs.
- Brick Joke: Many times during the series do the organic beings express exasperation when Data is too precise or elaborates too much. It's quite something else when the Enterprise's computer does so while he is expressing wonder at talking to himself.
- Combat Medic: Doctor Crusher, with her prescription of a phaser set to kill.
- Curb-Stomp Battle: When Quinn faces Worf, the showdown between them is given the weight of an act break, implying that they're about to have an epic battle. Instead, Work puts up less of a fight than Riker and gets tossed over a table almost immediately.
- Darker and Edgier: This is an unusual TNG episode. Besides the graphic violence during the climax, the tone is consistently tense, the threat quite insidious, and Starfleet officers are basically shooting at each other.
- Deadpan Snarker: When Worf asks if he's all right, Geordi replies that if he could see, he'd be seeing stars.
- Dynamic Entry: During the fight scene with Quinn vs Riker, La Forge, and Worf, Quinn is blasted by a phaser by an unseen assailant on the other side of a doorway. One camera cut later, and a quietly furious-looking Doctor Crusher is standing in the corridor with a phaser.
- Early Installment Weirdness: Picard dispenses water from a small decanter set out in his quarters. No only is this odd because the decanter is the exact same size as his glass, but it's also made more clear in later episodes that the crew receive all their food and beverages outside of 10-Forward from the replicators. There's no reason for Picard to keep a glass of water stagnating at room temperature when he could instantly order a fresh glass at whatever temperature he specifies. This is before Picard's trademark demand to the replicator for "tea, Earl Grey, hot."
- The End... Or Is It?: The final scene is Data reporting to Picard about the beacon and viewers hearing the signal.
- Fake Defector: Riker fakes being infected by the slugs so he can get into the conference room and help Picard. It fools everybody, Picard included.
- Gorn: The death and destruction of Remmick and the mother parasite inside him was very controversial when it first aired. The BBC cut several minutes of footage when first airing this episode in the United Kingdom, notably this part, and Canada's Space network preceded the episode with a viewer discretion warning, the only episode of The Next Generation to receive one. The episode did win an Emmy Award for Outstanding Achievement in Makeup for a Series, though.
- Hates Baths: Worf's dislike of bathing extends to swimming of all sorts.
- Hope Spot: Picard has one when he's trying to escape from a room of possessed admirals and runs into Riker, only to discover that he's possessed, too. Subverted, though, when Riker reveals that he was only acting possessed so he could get close enough to shoot the admirals.
- Keystone Army: The parasites are unable to survive after the mother parasite is destroyed.
- Literal-Minded: Data, as usual, regarding the experience of swimming in a real ocean vs. one on the holodeck.Troi: Have you ever been for a real moonlight swim?
Data: One can swim in moonlight?
- Make It Look Like an Accident: Shortly after Keel meets with Picard, his ship is found destroyed. When Picard asks, one of the mind-controlled Admirals says it was caused by "an implosion", and blames Keel's incompetence for the accident (after Picard has spent the whole episode talking up Captain Keel as one of Starfleet's best). In addition, several other officers have died off-screen in what were supposed to look like accidents.
- The Main Characters Do Everything: Riker calls for security while fighting with Quinn. Who responds? Worf and conn officer Geordi, but not a single security guard.
- Nice Job Fixing It, Villain!: The possessed Quinn initially came aboard the Enterprise in order to place Dr. Crusher under parasite control. However, he shows it off to Riker on the grounds that it likes him, which leads to the crew finding out what's really going on.
- No Sense of Velocity: Early in the episode, Riker tells LaForge to increase speed to Warp 6, and he replies "Aye, sir. Full impulse." Errrr... the man said warp, Geordi.
- Obvious Stunt Double: Not a lot of effort is made to conceal the fact that both Riker and Quinn are played by stunt doubles during most their fight. It's much easier to spot in the modern, remastered edition than it probably was on a standard-def television in the 1980s, however.
- Only a Flesh Wound: Geordi is thrown through a closed door, landing in the corridor along with both halves of the door. He's on his feet again a minute later and reports back to the bridge after a quick visit to sickbay.
- Orphaned Punchline: After the opening First Officer's Log, we pick up the end of a humorous anecdote Geordi is telling to Data. Data responds by explaining the joke and giving a rather creepy laugh.
- Parasitic Horror: The parasites are played for various types of horror: firstly, they change people's personalities, secondly, they make people violent and super strong, thirdly they themselves look pretty gross with their appendages sticking out of the person's neck, and fourthly, some of them breed in somebody's stomach, causing him to explode.
- The Power of Friendship: Picard initially has his doubts about the conspiracy theory, but he implicitly trusts Keel—calling him a lifelong friend along with Jack Crusher.Picard: Friendship must dare to risk, Counselor, or it isn't friendship.
- The Power of Trust: Keel and the others warn Picard not to trust anyone, as there's no way to be sure a person is who they say they are. note However, Picard trusts his crew unconditionally.
- Punch Catch: Quinn does this successfully with Riker twice. First Riker throws a punch after Quinn painfully grabs his arm. Then as he picks himself off the ground Riker throws another punch which Quinn catches, knocks aside, and viciously backhands Riker.
- Punch! Punch! Punch! Uh Oh...: Neither Worf nor Riker succeeds in causing any damage to the possessed Quinn.
- The Reveal: Captain Scott was under parasite control the entire time.
- Riddle for the Ages: The signal sent to a remote area of the galaxy by the parasitic aliens at the end is never brought up again in the series. Plans to pick the thread back up eventually got shifted into the Borg.
- Right Hand vs. Left Hand: Data uses this analogy when describing the clandestine orders he discovered.
- Ripped from the Headlines: This episode was meant to be a commentary on the Iran/Contra scandal.
- Running Gag: Data is once again getting shushed by people for rambling on. This time, it's because he gives an excessive number of synonyms to explain himself. Riker first cuts him off, and then even the ship's computer does it.
- Sequel Hook: A followup episode was planned, as the end seems to strongly suggest, but elements of it were instead folded into the Borg stories.
- Someone in the scriptwriting team of the series seems to be a big fan of Albedo: Erma Felna EDF, a furry comic, as two members of Starfleet (whose names appears in the Command Order) are named Itzak Arrat and Toki. In Albedo, Arrat is also a spaceship captain and Toki is the main heroine's best friend (who happens to be female).
- Keel's ship is the USS Horatio.
- Spotting the Thread: Picard's admiral buddy Quinn tells him and Riker that his mental fatigue was due to "difficulty assimilating other races into the Federation". It's treated as a Wham Line, triggering "Something is dreadfully wrong" music and Picard telling Riker that Quinn is Not Himself. Note that this is before the Borg gave "assimilate" such an ominous connotation.
- Squick: Characters react with in-universe revulsion several times.
- The parasites gorge themselves on live mealworms. When Riker is expected to eat them, he can't help but look revolted and chooses this moment to break his charade.
- Commander Remmick's head explodes under continuous phaser fire, causing the mother alien to burst from his ribcage. Picard is so revulsed by the creature that he uncharacteristically starts blasting it.
- Stock Footage: An establishing shot of Starfleet Command (a combination of miniatures, matte painting and live action extras) is recycled from Star Trek IV: The Voyage Home.
- Story-Breaker Power: Invoked. It's why Picard has Data review six months worth of Starfleet directives. With his ability to go over information at such a fast rate, Data can see questionable patterns that anyone else would've missed. When he is done, he is absolutely certain there is a conspiracy at work.
- Stun Guns: Crusher stuns Quinn after multiple attempts. She later advises Picard to use the kill setting because the creatures are so resistant to stunning.
- Surprisingly Good Foreign Language: Perhaps Jonathan Farwell (Walker Keel) is not really fluent in French, but his pronounciation of "Jean-Luc" is correct, au contraire to many actors on this show.
- Thinking Out Loud: Data discovers a new human idiosyncrasy.Data: Startling. Quite extraordinary, in fact.
Computer: Directions unclear. Please repeat request.
Data: That was not a request. I was simply...talking to myself. A human idiosyncrasy, triggered by fascination with a particular set of facts. Or sometimes brought about by senility. Or used as a means of weighing information before reaching a conclusion. Or, as a—
Computer: Thank you, sir. I comprehend.
- Tidally Locked Planet: Dytallix B was a world inhabited only by the Dytallix Mining Company. Due to the temperature extremes on either face of the planet, the company placed its facilities in the twilight region.
- Took a Level in Badass: Thanks to the aliens, an old man like Quinn has augmented strength.
- Trust Password: Keel tests Picard about their shared history, as apparently those who are infected by the parasites can't access personal memories. Keel says that other officers he suspected were bluffing their way through talks of old times.
- Violence Is the Only Option: While Picard always seeks to find a diplomatic solution first, he's moved by necessity and revulsion to simply kill the mother brain slug, which he laments in his final narration.
- What Happened to the Mouse?:
- Other than Quinn, it's not made clear if the other people the parasites infected survived.
- We've never found out what happened with the signal Remmick sent.
- The Worf Effect: The possessed Admiral Quinn easily hurls Worf over a table. Even Riker puts up a better fight than he does.