The Enterprise is underway. Captain Picard looks worried, and Troi can tell. She asks whether he's worried for Worf or for Riker, and he replies, "Both." And for good reason, since the crewmembers in question appear to be stranded in a mysterious jungle, where they come across some rather industrial-looking ruins, full of rusty girders and exposed piping. While Riker keeps a lookout, Worf creeps down and growls in satisfaction to find a weapon—a spiky gauntlet. Suddenly, they're attacked by a mace-wielding bug-faced Ninja Turtle, and a Skeletor lookalike with an ax! They fight off the foes, but it seems Worf's blood is up; he menaces his commander with the ax until Riker sharply orders him to stand down, "the exercise is over." Turns out they were on the holodeck the whole time! Apparently, this is how Klingons do "calisthenics," except the sessions where Worf doesn't invite any humans along are even more intense.The Enterprise encounters a patch of space which is completely black, with no stars visible. As they investigate it (it swallows two probes without a trace), Worf is reminded of an old Klingon legend about a space monster that devours ships. Suddenly the Enterprise is engulfed in the blackness. When they try to leave, they find they can't get anywhere, which they discover when they drop a probe behind them, and come up on the same probe up ahead. Then a Romulan Warbird appears and fires upon them, but is immediately felled with one photon torpedo, leaving no debris. They are further toyed with inside the anomaly with what appears to be another Galaxy-class Federation starship, the USS Yamato. No life signs are detected, so Riker and Worf beam aboard the Yamato, aiming for the bridge. However, they each materialize on different parts of the ship, in the corridors. Nothing is the way it is supposed to be, but they both end up on the bridge eventually, only to discover another, identical bridge, with them on it, through one of the doors. This causes Worf to start shouting, "There is ONE BRIDGE! ONE BRIDGE!" and Riker has to calm him down. Again.While this is going on, Picard notices a small opening in the blackness, where they can see stars and normal space. But with Riker and Worf on the Yamato, and unable to establish a transporter lock, they cannot head for it without leaving Riker and Worf behind. They finally get Riker and Worf back just as the Yamato starts fading into nothingness. When they make for the opening, it closes. They try again, without success, and finally clue into the fact that they're being toyed with and experimented upon, like rats in a maze. They're then confronted by an alien being that calls himself "Nagilum". He is curious about humanoids and the fact that they die, and wishes to conduct experiments on how they react to it. He kills the redshirted pilot on the spot. He becomes curious about Dr. Pulaski next, saying that she's different from the other (male) bridge crew members (although Troi is on the bridge as well, and Worf is also obviously different), and when it is explained that she is female and having both male and female is how they propagate the species, Nagilum requests a demonstration but is told no. He then says that he'll need to study "all kinds" of death, and the experiments he wants to conduct should only take about a third of the Enterprise's crew. Picard decides to set the ship to Autodestruct to thwart Nagilum's plans.While the Autodestruct counts down, Troi and Data go to Picard's quarters and talk to him about Death, telling him "You shouldn't be doing this. It is wrong of you [to decide for the rest of the crew], Jean-luc." Picard remarks that neither of them should be acting this way, and gets the computer to confirm that Data is actually on the bridge, whereupon they both vanish. To which Picard says, "Nice try, Nagilum."Nagilum finally acquiesces and backs out on his desire to conduct his experiments. Picard cancels the autodestruct, and Nagilum remarks that Humans and his species are too different to hang out together. Picard says, "We do have one thing in common. Curiosity." Nagilum says, "The point is well taken, Captain!" and chuckles. The episode ends with Picard saying, "We will meet again, but next time, it will be out there."
Tropes in this episode:
- Bizarrchitecture: As Riker and Worf investigate the phantom Yamato ship inside the void, the rooms themselves change around them and do not obey the laws of physics.
- Black Dude Dies First: Wesley inexplicably leaves his station early in the episode and is replaced by Ensign Haskell, a black Red Shirt. Guess who's the first person Nagilum kills.
- Blue and Orange Morality: Nagilum has literally no concept of human morality or ethics and sees nothing wrong with killing half the Enterprise crew to observe how they die to satisfy its own curiosity.
- Bottle Episode: Most of the episode takes place on the bridge, and the Yamato uses the same sets as the Enterprise to good and creepy effect. The only "new" set is the holodeck, and even that is a redress of an existing set. The major difficulty for the crew was keeping the bridge looking interesting for the whole episode, and to that end the actors were instructed to move around more than usual, and many new camera angles were experimented with.
- Captain Obvious: Riker, when he is beamed into a hallway on the Yamato instead of on the bridge: "This isn't the bridge."
- Cooldown Hug: Not a hug, but twice in the episode Riker has to calm an enraged Worf. "AT EASE, LIEUTENANT!"
- Danger Room Cold Open: Riker and Worf's apparent "away mission" prior to the opening credits, complete with a fight against a pair of aliens, turns out to merely be a session of "Klingon calisthenics" on the holodeck.
- Early Installment Weirdness: Kirk and crew encountered a similar void in space 97 years earlier, despite the fact that Data claims such an area had never been encountered before. This probably has to do with Gene Roddenberry's attitude that the only things he really considered in canon at this point were the movies (like the lack of familiarity with Kirk and usage of the movie-era Enterprise image in "The Naked Now").
- Eldritch Abomination: Nagilum practically is one, especially in Klingon myth.
- Eldritch Location: The void is a "hole" in space with no discernible physical proportions (dimensions, volume, etc.). When the Enterprise is trapped inside it, any attempt to escape it gets them nowhere, as they simply circle back to the same point despite flying dead-ahead. Then phantom ships start showing up with similar impossibilities to them, and the void turns out to be the home of a sentient, eternal, and amoral space being called Nagilum.
- Flanderization: Worf suffers badly from it in this episode, acting more like "an easily confused baboon" as SF Debris put it.
- Purple Is the New Black: The "hole in space", from which supposedly no light or other sensor readings can escape, is mostly a cloudy dark blue rather than pure black as would be expected.
- Skull for a Head: One of the monsters that Worf fights in his holodeck adventure has a very skull-like head.