You might have noticed a pattern this season in which intense, grim episodes (the sort with the Gorn and zombies) alternate with lighter installments (the sort with prototype holodecks and mischievous space imps). And while the lighter episodes have dealt with some serious matters and weighty emotions between the comic beats, the graver episodes have been, well, pretty grave. In other words, attentive viewers will already know to brace themselves before “Through the Lens of Time” begins.

That it opens with narration from Ensign Gamble, an endearing recent addition, feels kind of ominous as well. Gamble has been hanging around for a few episodes, brightening up scenes with his unabashed enthusiasm for Starfleet in general and his assignment on the Enterprise in particular. That the focus should fall on him right away suggests he’s about to take center stage for an episode, which isn’t always such a good thing for supporting Star Trek characters. “Today started out like any day here, me working in sick bay,” Gamble says. “But after today, I know my life is never going to be the same again.” He’s right but not in the way he thinks, unfortunately.

Gamble is excited because he’s joining his first away mission. (His voice-over apparently dates from after the episode’s first scene but before, well, the bad stuff happens.) It’s a trip accompanying Christine and Dr. Korby to a ruin that could support a Korby theory that, in Gamble’s words, “ancient man’s fascination with resurrection and reincarnation could all be based on forgotten technology.” This sounds exciting, and Gamble’s enthusiasm proves infectious, inspiring a big grin from Dr. M’Benga as he hands Gamble some duties to take care of before he leaves.

Korby’s excited too but also a bit anxious. Their destination is a sacred site for the people of M’Kroon, who aren’t too thrilled about this expedition, which involves using the Enterprise itself as a kind of ultrapowerful shovel (to use the scientific term). Christine gives Korby crap about his worrying, but it comes from a loving place. Which isn’t to say she doesn’t still worry about her ex’s feelings. Though La’an attempts to breeze past her, Christine matches her pace to ask about Spock’s well-being and his feelings about Korby. La’an immediately tries to let her know she wants no part of any drama and would prefer if Christine didn’t “make it weird.” Besides, she and Spock are keeping it casual and if Christine is worried about Spock, especially Spock being weird about Korby, she should talk to him directly, a sentiment La’an delivers clearly but politely.

The expression on Christine’s face as she nods says she knows it’s not quite that simple, a notion confirmed by a later awkward elevator ride in which she brings up his new relationship with La’an. “She is an excellent dance instructor,” Spock replies, a deflection that neither acknowledges nor denies what’s going on between lessons. As for he and Korby, though Spock says Christine’s use of the word friendship to describe the status between her old boyfriend and her current one is “a relative term,” Spock assures her he has made sure all will go smoothly.

Gamble’s duties before beaming down include a check-in with Marie who, by all appearances, is doing great in fighting off the infectious Gorn presence thanks to the combined efforts of Spock and M’Benga. (Of course, she seemed to be doing great before and we know how that turned out.) Gamble barely has time to relay this to M’Benga before the doctor hits him with some good news of his own. After many past requests, Gamble is joining the away mission!

In the mission briefing, Spock announces his intentions to monitor the landing party’s progress from the Enterprise, while Beto’s continuing documentary work draws, let’s say, a mixed response from the others. Pike is annoyed by the camera, but Pelia could not be happier to be an active participant in the project. Despite Pike’s reservations, Beto’s assignment means he too will be going down to the surface alongside Gamble, Christine, and Uhura, whose communications skills may prove useful in translating whatever they may find there. They’re joined by N’Jal (Ish Morris), a stone-faced M’Kroon who does not like to shake hands. After some preparations — and fairly intense flirting between Beto and Uhura — it’s time to hit the planet with a well-measured deflector beam. This reveals an unexpectedly huge structure, prompting Christine to tell Pike, “We’re gonna need a bigger landing party.” This will prove to be something of an understatement.

This also blows up Spock’s plan to chill on the Enterprise during the expedition. Though the ship can’t provide a huge landing party thanks to the M’Kroons’ veto, Christine’s request brings both Spock and La’an. Here we learn a bit more about why this spot is so important to Korby and Christine, who have followed a string of clues to this discovery that they hope will prove the M’Kroon are descended from “an advanced civilization that could travel across multiple galaxies.” Or, as Gamble puts it, they might have been “ancient astronauts.” Complicating this: the ancient civilization’s claim to have achieved immortality. This, in turn, may have something to do with “creating quantum instability at a molecular level.”

All this will sort of become clearer over the course of the episode but, most immediately, they have to figure out how to get inside, which Uhura has determined has something to do with “blood given freely.” In essence, the mission has turned them all into Indiana Jones–Lara Croft–Nathan Drake, and they have to untangle clues, puzzles, and traps if they’re going to raid this tomb (in an ethical, culturally respectful, and scientifically minded Starfleet way). A drop of Christine Chapel’s blood turns out to meet the “blood given freely” requirement, and briefly, this looks like it’ll be a pretty simple mission. That feeling doesn’t last.

A corpse provides the first sign of trouble. It’s centuries old, but Spock suggests this may be a good time to beat feet, tell the Enterprise what’s up, and reassess their approach, especially since they can’t beam out from inside the chamber. Spock defers to N’Jal, who would like to press on for the sake of his people, and what follows almost immediately calls the wisdom of this decision into question. While Korby and Christine check out a “memory stone,” Gamble picks up a pretty, glowing orb, which almost immediately explodes in his face and destroys his eyes, in the process creating what has to be one of the most disturbing images ever seen in an episode of Star Trek.

Things don’t immediately look dire for Gamble, who’s whisked out of the chamber, up to sick bay, and into the care of M’Benga, who sets to work generating a new set of eyes. Nonetheless, Christine decides it’s time to pull the plug on the mission. Unswayed, Korby and N’Jal choose to stay behind. The question, however, soon becomes moot. After peering into the structure’s next chamber via drone camera, N’Jal panics and tries to flee, a fatal decision that closes off the door for anyone else who wants to escape. The choice of whether to stay or go is taken from them.

Instead, they have another choice. Stay put, which didn’t seem to work out so well for the corpse they found, or explore the next chamber (once Christine nervously unlocks it). But when they head in, something odd happens. The landing team is separated into parties of two: Uhura and Beto, Spock and Korby, and Christine and La’an. (At least one of these pairings wants to spend more time together. The other two, less so.) Each party can talk among themselves but can’t see or reconnect with the others. It’s puzzling.

Also puzzling: Why can’t M’Benga heal Gamble? “It’s no secret I’m fond of the boy,” M’Benga tells Pike, but that just makes his failure hit even harder. What’s more, Gamble starts behaving strangely, which jibes with M’Benga’s theory that some kind of invasive substance is preventing his eyes from regenerating. Worse still, scans show portions of Gamble’s brain have died, which sends the ensign into a panic.

On the surface, the paired-off crew members have other problems. La’an and Christine have found a sculpture surrounded by writing, including some Chinese characters, that’s both there and not there on the quantum level. Nearby (maybe extremely nearby), Spock and Korby explore their space. While Korby translates the memory stone (and ominously encounters vezda, the M’Kroon word for “evils”), Spock dons the corpse’s protective eyewear and discovers thousands of the little glowing orbs that blinded Gamble inside the structure at the center of the room, including one that offers a vision of an attacking Gorn. He’s understandably alarmed, as are Pike and others aboard the Enterprise when they analyze the remains of Gamble’s orb, which Pelia describes as older than anything she’s ever seen. Also: It gives her the “heebie-jeebies.”

These heebie-jeebies inspire Pike to check on Gamble’s status. Whatever has taken over Gamble’s brain starts to taunt M’Benga about Rukiya, the daughter whose life he saved but who left him for the stars. When Marie arrives in sick bay with a migraine, she and the entity inside Gamble seem to recognize each other and, after exchanging a few words (in Gornish?), they begin to fight. Marie gets the better of her adversary but can’t stop him from escaping. She also doesn’t seem quite herself as M’Benga administers a sedative. When he catches up with Gamble, the ensign has taken a hostage and seems to be flitting between his own sweet personality and whatever has taken hold of him. M’Benga makes the difficult decision to send Gamble, or whatever, to the brig.

On the surface, each team talks to one another and shares their discoveries, including Uhura’s revelation that they’re all still somehow in the first chamber together. After hearing about the inscription, which includes the words parasite and hitchhikers, they construct a hypothesis that an attempt at immortality had the Event Horizon–like side effect of bringing something really, really bad into their dimension. Maybe, La’an posits, they’re in some kind of prison. By putting all the right pieces in the right places, Christine reunites the party, which still faces the problem of finding a way out. It’s pretty simple, really: All they have to do is accept that they’re in an environment where effect precedes cause and walk across the empty space to turn on the bridge that will allow them to cross. Or to have crossed. It’s confusing! Fortunately, it works, allowing them to leave the horrors of wherever they just were behind.

The brig, it turns out, isn’t strong enough to hold whatever Gamble has become, and he escapes and holds Pelia, Scotty, and Sam at phaserpoint. Though Gamble’s personality seems to be struggling with the Vezda Entity within, Pelia ultimately makes the tough decision to put him down, freeing the malevolent entity, which Scotty subsequently captures in one of the orbs and then transports to, as he puts it, “nowhere.”

This turns out, as Spock and Christine confirm, to be a transport buffer, the safest place to store this kind of malevolent entity. (But is it?) Meanwhile, the M’Kroon will work with the Federation to contain the entities on the surface. (But can they?) “Were they evil, Captain?” Beto asks. “Good and evil are relative terms, son,” Pike replies, prompting a rebuttal from Pelia, who firmly believes the universe contains good and evil. After elaborating on this via dramatic monologue, she asks Beto if he needs another take for the movie. It’s a funny moment, but it doesn’t quite blunt the creepiness of what she’s saying. It’s enough, in other words, to give anyone the heebie-jeebies, a feeling only reinforced by the blinking control panel labeled “Vezda Entity” behind M’Benga as he breaks the bad news to Gamble’s family.

This was a rough one. Good episode, but rough! Gamble was a charming character while he lasted, and it’s unclear whether his death raises or lowers the threat level for other recent additions. (Beto? The three-armed bartender?) It’s also the second episode this season that provides just enough Star Trek science to paper over what’s essentially a horror plot. We had zombies two episodes ago. Now the Enterprise has to deal with some kind of malevolent immortal entity with a tendency to taunt its adversaries with dark moments from their past, à la The Exorcist. It’s not exactly a new flavor for Strange New Worlds to dish out; the Gorn have paid homage to the Alien films since their reintroduction. But the horror elements have started to accumulate, and the horrific threats don’t go away. The Gorn have retreated, but something’s still going on with Marie. And I wouldn’t put a lot of money on this Vezda Entity staying in stasis.

Hit It!

• “I hear the M’Kroon have a unique vocal range.” Good recovery. RIP, Gamble. You will be missed.

• Pelia and Scotty have quietly become the series’ most reliable comedy team. Keep an eye on Martin Quinn’s face whenever Carol Kane does, well, anything.

• So what’s going on with Captain Batel? Marie’s health is up one episode, then down the next, but there’s obviously something all the medical treatment has yet to address.

• What are the odds that we see Beto’s in-progress film in the form of an episode? Pretty high, I’d wager.

 Attentive viewers will know to brace themselves before this episode begins.