Star Trek: Lower Decks And T'Lyn: Everything To Remember About The Newest Crew Member

This post contains spoilers for "Star Trek: Lower Decks" season 4.

When the Lower Deckers returned this week for "Star Trek: Lower Decks" season 4, a few things about our favorite underdog crew looked different. For starters, they're not actually Lower Deckers anymore — Tendi (Noel Wells), Mariner (Tawny Newsome), and Boimler (Jack Quaid) all receive promotions to lower-tier mid-level officer positions in the premiere, with Rutherford (Eugene Cordero) soon following. But there's also a change to the main crew's roster, as Vulcan T'Lyn (Gabrielle Ruiz) appears alongside the main cast — with little explanation for folks who might not remember her.

In the premiere episode, T'Lyn is clearly already part of the Lower Decks team, but she's still finding her footing within the tight-knit group and they're still adapting to hanging out with an extra-blunt Vulcan. In her re-introductory scene, Tendi hypes up their hydrogen sample project with signature cheer ("Hydrogen is the most common element in the universe," T'Lyn helpfully notes) while Boimler doesn't know how to respond when she points out how smelly he'll be after holodeck cleaning duty. T'Lyn isn't great at small talk, but "Star Trek: Lower Decks" makes a great decision throwing her into the show's typical chaos with little preamble, as her problem-solving personality is perfect for disaster scenarios.

While T'Lyn has stayed relatively mum about her personal life so far this season, viewers actually got a glimpse into her pre-Cerritos work posting way back in season 2. In the episode "wej Duj," the action is split between the lower decks of the Cerritos, a Klingon Bird-of-Prey, and a Vulcan vessel, showing the thankless work of underlings across several species. Among them is T'Lyn, who immediately raises red flags among her teammates when she goes above and beyond in her basic duties, creating a new long-range sensor algorithm when she was meant to be simply monitoring the system that was already in place.

Anyone who has worked within a bureaucratic system and tried to make it more efficient will relate to T'Lyn's go-getter approach to her work, but her Vulcan colleagues see her choice to go slightly off book as insubordination and individuality. They repeatedly chastise her for using the wrong language — she mentions "belief," gut feelings, and her own desires whereas Vulcans are used to hearing about only logic — and force her to meditate to improve her self-control. During the climax of the episode, T'Lyn saves her crew's life with an untested program she created in her spare time, but is reassigned to another ship as punishment for her impulsivity.

When this episode first aired, T'Lyn's plot felt like a running joke about how subdued Vulcans are as a rule, as T'Lyn's superiors respond to her measured comments as if she's throwing a tantrum. Now that we know she's set to become a main character, though, we can learn a lot about her from looking back at "wej Duj." It's clear that T'Lyn's curiosity drives her, as she openly expresses her displeasure with a system that forces her to follow rules that limit her own learning. "Logic is the beginning of wisdom, not the end," she says, and it's a quote that we've heard before — from Spock himself.

For some reason, T'Lyn didn't actually show up in "Lower Decks" again until the third season finale, when Tendi learned she'd be working alongside the Vulcan as a fellow science officer. T'Lyn seemed to be new to the Cerritos at the time, so we haven't yet learned about what she was up to during season 3, but it's obvious that she and Tendi are the same type of spirited, curiosity-driven geek. Perhaps T'Lyn just joined the Lower Deckers now because the show wanted the chance to get a Vulcan in the mix, or perhaps she'll shake up the core group's dynamic in a major way. Regardless, if T'Lyn wants to be able to break the rules to make the world a better place, she's certainly come to the right place.

New episodes of "Star Trek: Lower Decks" stream Thursdays on Paramount+.