Star Trek: Lower Decks season 4 episode 8, “Caves,” asks, “You ever been trapped in a sentient cave? That’s a dark place that knows things!” The anthology episode was written by Edgar Momplaisir and directed by Bob Suarez. 

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The USS Cerritos is in orbit around Grottonus. Lt. JG Beckett Mariner (Tawny Newsome) arrives in the transporter bay and is delighted to find Lt. JG Bradward Boimler (Jack Quaid). Boimler laments that they never get paired together anymore. But that’s when the away team is rounded out by Lt. JGs Samanthan Rutherford (Eugene Cordero) and D’Vana Tendi (Noël Wells). The quartet celebrates the Beta Shift reunion.

Eugene Cordero as Rutherford, Noel Wells as D'Vana Tendi, Jack Quaid as Brad Boimler and Tawny Newsome as Beckett Mariner

Photos: Paramount+

Tendi reveals the mission involves researching moss in a cave. Mariner bemoans the involvement of caves as they beam down. Rutherford and Tendi frolic away. Boimler admits caves do all look the same. Rutherford and Tendi remain excited. But Mariner says they should hurry up, as nothing good ever comes from a cave mission. She says it feels like a third of their missions are in caves. Boimler says caves are peaceful and quiet.

But then an incoming transmission from Commander Jack Ransom (Jerry O’Connell) warns of detected tremors. The cave begins to collapse. As they are engulfed in darkness, Mariner says, “Oh yes,” says Mariner. “So peaceful.” Boimler agrees, “Stupid cave mission.”


Rutherford activates a light on his implant. Everyone’s okay, but “trapped in a cave with no way to communicate.” Mariner says any unspeakable evils in the cave can skip past the waiting and just attack them now. Boimler attempts to call for an evac but has no signal. Mariner kicks the moss and it illuminates. Tendi observes the reaction and begins scanning. Rutherford turns off his light and uses his implant to scan the area.

Tendi (Noël Wells) has her shoe eaten by the moss.

The illuminating moss begins to follow Mariner. Tendi wonders if it might be drawn to her body heat. However, the moss attacks and eats Tendi’s shoe. Now facing carnivorous moving moss, Boimler says they only have so long to escape. Rutherford suggests that their shared experience in cave missions might hold the answer. Tendi brings up a time after the rage virus. But Mariner says that was a turbolift, not a cave, and therefore a different situation. 

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Boimler realizes he has a relevant story. He and Steve Levy (Fred Tatasciore) recently got caught in a cave and used gannimite to boost their comm signal. A flashback set on Kyron 4 begins. Boimler says the mission started as a regular Dilithium survey, but then an ion storm blew in. Boimler and Levy seek shelter from the storm in a cave, but the rock blocks their comms. Levy asks Boimler if he knows why they don’t make unblockable comms. Boimler postulates it is because the tech isn’t advanced enough. Levy asserts that it’s “because of what they don’t want us to hear.”

Boimler says they need to find a way out. Levy suggests they wait out the storm. Boimler replies that the briefing says storms can last years. Levy says he prefers to take in the mission with his own eyes.

Vendorian Morality Test

When they think they hear something, Levy says it feels like a Vendorian trap. Boimler says that’s nonsensical. Levy says that’s what they want him to think, and continues that they’re shapeshifters.

Levy (Fred Tatasciore) and Boimler (Jack Quaid) explore a cave.

Boimler’s scan picks up a faint energy signal. Levy protests and says that’s what the Vendorians want. Boimler denies the presence of Vendorians. He further chides Levy for buying into the stereotype. Levy holds steadfastly to his beliefs. Under protest, Levy continues to follow Boimler to the energy source. They find a one-person ATV. Boimler says one of them will have to stay behind. But Levy destroys the ATV with his phaser. This causes a cave-in.

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Boimler asks what he was thinking. Levy asserts that a “dream vehicle” sitting in the middle of a cavern is obviously bait for “a classic Vendorian morality test.” Boimler grows frustrated. He says he knows Levy is a math genius. But he asks him if he has any “wild, unfounded theories” on why he has been stuck at the same rank for a decade. Boimler says it’s because he’s insufferable. He proceeds to denounce three of Levy’s favorite theories as untrue. Boimler says everyone benefits from them being stuck in the cave, since they don’t have to deal with Levy.

Levy’s eyes tear up as he says he just wants to help. But then many nearby stalagmites are revealed to be disguised Vendorians. The Vendorians tie up Levy and Boimler and drag them to a hole. The Vendorians say that the pair will be punished for arguing rather than collaborating. Levy declares that the Vendorians are going to lay their egg pods inside Levy and Boimler. Then they’ll have to look each other in the eye as they burst from their chests.

Delicious Crickets

“You know of our customs?” asks one of the Vendorians. Boimler says he’s Levy’s a huge Vendorian fan. The Vendorians are won over by Levy. They assert his “knowledge is artfully mixed with hyperbole and fiction.” 

Boimler (Jack Quaid) and Levy (Fred Tatasciore) eat giant crickets with the Vendorians.

Levy says after sharing a meal of giant crickets with the Vendorians, they don’t seem so scary. Boimler says Levy is still a crackpot with dangerous ideas. However, Boimler has learned not to yell at him, or something. Levy says they’re friends and Boimler attempts to deny this. But the Vendorians celebrate that enemies have become friends. They declare the morality gambit a success. The Vendorians lift Boimler and Levy as they celebrate.

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Back in the cave on Grottonus, Boimler concludes his story by saying the Vendorians taught him to use gammonite to boost comms. Mariner expresses disbelief that Boimler befriended Levy. Boimler says Levy’s not so bad and admits they subsequently hung out together on the holodeck. Rutherford and Tendi are shocked. Tendi says that sometimes being stuck together can lead to surprising conversations. She begins to tell her turbolift story. But Mariner cuts her off again. They’re interrupted when the moss spits a skeleton toward them. Mariner accuses the moss of wasting bones (MOOPSY).

Tendi (Noël Wells) and Mariner (Tawny Newsome) use their phasers in a cave.

Boimler’s tricorder scan finds trigammonite. He states this could be used to boost comms too. They just need to separate it. Rutherford has an idea and asks for Boimler’s pants. Without hesitation, Boimler complies. Rutherford says the material of the uniform could disperse some of the energy of a phaser blast. He instructs Mariner to bounce her phaser beam off a stalactite to hit the pants. This causes the pants to disintegrate and leave trigammonite behind.

Shades of Horta

Rutherford begins to harvest the trigammonite. He says he learned how to do stuff like this when he was trapped in a cave with Doctor T’Ana (Gillian Vigman) and their kid. The other three are shocked he had a cave baby and didn’t tell them. A flashback to Balkus 9 begins. Rutherford was assigned to join T’Ana in gathering some ferns. T’Ana is unimpressed by the enthusiasm of their guide.

Ritherford (Eugene Cordero) and Doctor T'Ana (Gillian Vigman) use their phasers in a cave.

Their guide shows them the location of the ferns in a pool of water. However, Rutherford’s tricorder scan picks up some strange vibrations. He wonders if they should evacuate. But their guide assures them this grotto hasn’t been home to the Graphlax for generations. She says many believe it is a myth. Then she is attacked by the Graphlax. 

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Rutherford and T’Ana fend off the Graphlax with their phasers. The guide says her body is done and she must travel to a new one. Rutherford reassures her. However, she “procreates her base mind via dermal contact” by pressing her hand to Rutherford’s face. Then she dies. Rutherford doesn’t feel so well. T’Ana reveals he’s pregnant. She explains that the species procreate via dermal contact, transferring “their consciousness into a protein mass which grows into a baby version of themselves in seconds.”

Rutherford says he isn’t comfortable with a lot of what’s going on. T’Ana says he’ll be saying that more soon. She delivers the baby by c-section then gives her to Rutherford to hold while she closes him up. Rutherford passes out.

Cave Baby

Rutherford awakens to find T’Ana unsuccessfully attempting to feed the baby. Fortunately, Rutherford has the knack of feeding her. T’Ana says their priority is protecting the baby from the Graphlax, followed by escaping from the cave. Rutherford calls dibs on the first babysitting shift. T’Ana says, “Good, because the only thing I hate more than engineers is babies.”

Rutherford (Eugene Cordero) holds the baby while Doctor T'Ana (Gillian Vigman) scowls.

Rutherford and T’Ana alternate between watching the baby and exploring the caves. As the baby grows more comfortable with them, they make dead ends with their phasers. T’Ana says she still doesn’t like babies but that this one is more of a “co-adventurer.” 

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However, that’s when the Graphlax reappears. Rutherford, T’Ana and the baby are cornered. But Rutherford pulls out his tricorder. Rutherford calibrates the tricorder to communicate with the Graphlax. The Graphlax says it only wants to protect its baby. It is revealed that the baby is inside the pool with the ferns. Rutherford says that they didn’t know that was its baby, and says if it lets them leave, they’ll make sure no one comes back.

T'Ana (Gillian Vigman), Rutherford and the Graphlax.

The Graphlax says it has been observing them. It concludes they are good parents and tells them to follow it. The Graphlax picks up its baby and begins leading the way. As they follow, T’Ana tells Rutherford that he’d “make a not-terrible father.” When Rutherford asks if this means he’s the first engineer she likes, she tells him to shut up.


In the present day, Mariner asks why Rutherford never told them about his kid. Rutherford replies that Boimler never told them about the Vendorians. Tendi tries to tell her turbolift story again, and Mariner stops her again. The cave makes a groaning noise as the moss grows closer. Mariner uses her comm badge as a filter for the trigammonite. Rutherford asks where Mariner learned this skill. Boimler says the way the stories are going, he wouldn’t be surprised if she “learned it from those creeps in Delta Shift.” Mariner concedes this. Boimler asks since when has she been friends with Delta Shift.

Mariner says since she was assigned to lead them on an away mission on Glish. However, their shuttle (Kings Canyon) was hit by a magnetic anomaly along the way. In a flashback, the KC crashes into a cave. Mariner is accompanied by Ensigns Karavitus (Artemis Pebdani), Asif (Asif Ali) and another Delta Shifter. Asif has a compound fracture. Mariner gives them assignments.

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The KC can be salvaged, but they need purgium to get the power started. Mariner’s scan reveals there’s a pile of it nearby. However, when she attempts to move towards it, she begins to rapidly age. The same effect happens to Karavitus when she attempts to join her. A scan reveals they’re being affected by a mineral vein that emits chronitons. As such, proximity to the vein will cause anything organic to experience a bio-temporal flux. Both Karavitus and Mariner begin racing toward the pergium. Soon they are elderly and still arguing.

Delta Shift

Karavitus says Mariner hates her because she’s Delta Shift. Mariner says she hates her because she’s an asshole. Furthermore, neither of them can help Asif if they’re both dead of old age. Karavitus says she’s only an asshole because she works just as hard as Mariner at the same jobs, but everyone’s indifferent. She says their shift sucks because no one’s awake. She’s only met the captain a few times, and that doesn’t afford any chance to rank up.

Asif (Asif Ali), Mariner (Tawny Newsome) and Karavitus (Artemis Pebdani) experience time distortion.

Mariner realizes they have different experiences aboard the Cerritos. She says she thought Delta Shift hated them because they had to fix everything Beta Shift broke during the day. Karavitus says that sucks too. Mariner apologizes for being a dick to her. They agree to try and find a shift between theirs where they can be civil to each other. If they can survive the stupid old-age cave.

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Mariner says they need someone younger. Karavitus declares Asif to be a child prodigy. Asif says his leg is broken. But Karavitus says it’ll heal with the time dilation. However, without medical treatment, his injury grows worse. Eventually, his leg falls out. Meanwhile, the other member of the away party has found pergium, over in a corner that makes you a little younger when you get close to it.

Mariner (Tawny Newsome) and Karavitus (Artemis Pebdani) in the King's Canyon shuttle.

Power is restored to the KC. Ransom contacts them and informs them they’re being rescued. Mariner joins everyone but Asif in a “Delta Shift” chant. Meanwhile, Asif begs them to go pick up his leg, in case they can’t grow him a new one (don’t worry, they can).

Sentient Cave

In the present, Rutherford and Boimler are offended that Mariner chanted with Delta Shift. Tendi asks them not to fight. But they angrily agree to get out of the cave and go their separate ways. However, when Rutherford attempts to contact the Cerritos, all four are pinned to the wall by moss. The moss says they cannot leave until they hear Tendi’s story. Tendi protests that it’s not even about caves but the moss (and Mariner) insist.

Boimler (Jack Quaid), Rutherford (Eugene Cordero), Mariner (Tawny Newsome) and Tendi (Noël Wells) are stuck to the cave wall with moss.

The story flashes back to Tendi’s first day on the Cerritos. After the events of “Second Contact,” Beta Shift throws back many rounds of drinks (while the Chu Chu Dance plays in the bar). As they leave, Mariner reveals she swapped the synthehol for actual alcohol. But as they ride the turbolift, a damaged power relay causes them to get trapped. A request to be beamed out is ignored.

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Two hours later, they play “TARG” with their socks. Three hours after that, they play twenty questions. Four hours after that, they’re piled in the center of the turbolift. Tendi says she was worried about being the only Orion on board since Orions have a reputation. Rutherford assures her that all they see is “a smart, capable, awesome ensign.” Tendi says she’s glad they’re friends. Then Shax tears open the doors and screams that he’s there to rescue them.

Jack Quaid as Brad Boimler, Tawny Newsome as Beckett Mariner, Eugene Cordero as Rutherford and Noel Wells as D'Vana Tendi. They're all locked in the Turbolift.

In the present day, all four laugh. Mariner apologizes for cutting off the story earlier. Tendi says it doesn’t matter if they start hanging out with other people or having a baby. They’ll always be friends. Tendi says she loves them.

New Friends

The moss says it has eaten many outsiders in the cave. But it has never made a friend. It asks if they can be friends. Tendi says of course. She tells it that they came in here to study it. The moss releases them. It tells them to take the scans, so long as they keep telling stories.

Mariner says they have plenty more cave stories. She mentions the sentient cave. Tendi begins telling a story about when they met their doppelgängers in a cave. The rest of Beta Shift joins in. 

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Across the cave, two stalagmites are revealed to be Vendorians. The Vendorians celebrate the fact that the junior officers have rekindled their friendship. “By not allowing their new responsibilities to destroy what is truly important, they have passed our test,” concludes one. The Vendorians decide to wait to unblock their communications so they can enjoy the moment a little longer. 

New episodes of Star Trek: Lower Decks are available for streaming on Paramount+ on Thursdays.

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