WARNING: The following contains spoilers for Star Trek: Discovery Season 4, Episode 7, "... But to Connect," streaming now on Paramount+.
The crew of the USS Discovery has been something of a revolving door throughout Season 4, with longtime crew members deciding to spend some time away from the starship's ongoing mission while others have decided to play a more active role under Captain Michael Burnham's leadership. And as Star Trek: Discovery Season 4 reaches its halfway point while continuing to investigate the mysterious dark matter anomaly, cutting a devastating path across the galaxy, it has just bid farewell another fan-favorite character for the foreseeable future while officially recognizing a surprise ally as a full member of the crew.
Ever since the Discovery's ship computer absorbed an extraterrestrial data repository, known as The Sphere, it began to develop sentience and her own personality as the ship was upgraded with 32nd-century technology. Now referring to herself as Zora, the computer has begun to noticeably display empathy towards human emotions and is able to defy even Burnham's direct orders as the Discovery continues its perilous investigation behind the source of the anomaly. While Starfleet and Chief Engineer Paul Stamets are initially wary that Zora could develop into a malevolent artificial intelligence, like the rogue program Control that menaced the galaxy in Discovery Season 2, Doctor Kovich's analysis reveals Zora is unlike any A.I., with Zora even capable of dreaming. With this in mind, Kovich and the crew welcome Zora as her own crew member as they continue their mission.
Zora's official, recognized admission onto the Discovery's crew as a new, unique life form, rather than simply being considered the ship's computer, is undercut by Gray Tal deciding to leave the starship for now. While Gray was never officially a Starfleet officer, he was a welcome presence and loving partner to Adira Tal. Though Gray's original, organic body was killed, leading Adira to bond with the Tal symbiont, Gray's consciousness was transferred into a synthetic body to allow him to interact with others rather than live on in Adira's mind. Gray decides to train to become a Trill Guardian, figures within Trill society safeguarding the symbionts and facilitating their bonding process with host bodies, resulting in him traveling to the Trill homeworld to undergo the extensive training.
This shake-up to the personnel on board the Discovery is only the latest change-up that the crew has seen over the course of Season 4. After spending several months helping the powerful Su'Kal acclimate into Kelpien society on Kaminar and serving as a respected senior advisor among the people of his homeworld, Saru returned to the Discovery, more confident and balanced by the experience while serving as Burnham's executive officer. Saru's return came shortly before Sylvia Tilly decided to leave the crew to serve as an instructor at the newly reopened Starfleet Academy after going through something of an existential crisis as she adjusted to life in the 32nd century. And while she only returned to the crew on a temporary basis, the Discovery welcomed back Engineer Jett Reno as she helped her old friends analyze data gathered from the anomaly.
Tilly and Gray's respective departures leave open the possibility for both characters to return to the Discovery in the future, neither parting of ways was an acrimonious, definitive split. Gray and Adira are continuing their romance long-distance while Tilly has quietly suggested that the chance to teach and inspire Starfleet's next generation of cadets could help her find her place in Starfleet and in relation to the Discovery. In the meantime, there are going to be some absences felt among the crew, even if Saru is back along with the increased prominence and recognition for Zora moving forward as Season 4 continues.
To see one crew member leave and another come aboard, Star Trek: Discovery Season 4 releases new episodes Thursdays on Paramount+.