The first officer of the U.S.S. Enterprise, “Number One” beams aboard the Discovery while the Enterprise is docked. She has been investigating the murder charges brought up against Spock. Like her Captain, “Number One” doesn’t believe Spock is guilty of these heinous charges. Convinced that something about the investigation isn’t adding up, she’s breached protocol to find Spock’s warp trail. Pike orders the Discovery to follow the trail, but their mission is soon halted when the ship gets caught in some kind of stasis field generated an enormous spherical entity. It is part organic and part technology, and before long it starts affecting the ship’s systems, starting with the universal translator.

With the crew and the ship all speaking different languages, Michael Burnham calls upon an ailing Saru to help. Fluent in 94 languages, Saru manages to communicate with the ship long enough to bring some semblance of normality back to the bridge. The rest of the ship is another matter. Burnham and Saru head down to each department to fix the universal translator. They succeed, but almost immediately, a conduit ruptures in Engineering, sending it into lockdown.



Saru, looking far worse for wear, is brought to Sickbay by Burnham. Dr. Pollard says the pain Saru is in would kill any other humanoid. The problem is, nobody knows much about Kelpians, but Saru keeps deflecting, showing more concern for the ship. With reason – it turns out that Saru’s condition is something Kelpians undergo, a terminal condition called vaharai that signals the end of a Kelpian’s life.



Down in Engineering, following ‘May’s recent extraction from Tilly, Stamets has been able to keep the mycelial symbiote encased, explaining that the spores consider the network their ‘home’. Tilly’s guilty conscience may have conjured her dead classmate, and now the fungus is connected to Tilly, even emulating her hand in an effort to comfort her. Commander Denise "Jett" Reno, who was rescued from the crashed U.S.S. Hiawatha, joins Tilly and Stamets and, though her methods may be unconventional, she does have some ingenious ideas on dealing with the symbiote. Unfortunately, they don’t exactly pan out and the symbiote escapes its cage.



Meanwhile, Saru surmises that by studying the virus they can generate digital antibodies. While working together, Saru apologizes to Burnham for not revealing his disease. He couldn’t bring himself to admit to a strong personality like Burnham that his species is geared to submit to their end. But Burnham insists they are friends, so he shouldn’t have dealt with this news on his own. Saru asks Burnham to catalog his logs and gives her a brief history of his life before Starfleet.



When Captain Georgiou came to his planet, Saru was granted refugee status in the Federation. This opportunity allowed him to meet alien beings and learn several languages, though he never shared his own language with others. Saru has made his life about helping people the way he was helped. Touched, Burnham tells Saru that she believes he’s the most empathic person she knows.



Burnham returns to the bridge where she learns that Spock’s warp trail is dissipating fast. If they aren’t able to break free soon, he’ll be lost to them for good. Pike has a plan to divert power from the deflector shield to the impulse engines, but the comms link to Engineering is down. Burnham volunteers to head down there herself and get them to do the job.



But she can’t even enter Engineering. The mycelial symbiote has attached itself to Tilly again, but Stamets and Reno can’t get it off her. Burnham wants to know what it wants but how will they find out? Stamets believes he can configure some tech to make the symbiote speak through Tilly, but the only way to do it requires him to drill a hole in her head.



This gives Burnham an idea. She runs back to Saru and they realize that the sphere has been trying to communicate with them this whole time. They rush to the bridge where Pike is ready to fire at the sphere. He is pressed for time as Spock’s warp trail is about to disappear. Saru pleads with Pike to halt, explaining that the ultraviolet rays he’s been seeing are from the virus infecting the sphere. The sphere is dying, just like Saru, and it wants to be remembered.



To allow the sphere to download its information on to Discovery, Pike has to drop the shields. This is a tough decision for him, but as scientists – explorers – this is an opportunity that can’t be missed. Reluctantly, Pike gives the order to drop the shields. The sphere downloads a tremendous amount of data onto the computers, but Discovery is still trapped in the stasis field. Bracing themselves for the end, the sphere implodes, yet with its last act, it pushes Discovery to safety.



Now, it’s Saru’s turn to say goodbye. The bridge crew stands to say farewell as Burnham takes Saru to his quarters.



Saru is disheartened that he left his heritage behind when he joined Starfleet. Burnham reminds him of all that he has achieved, but kind words cannot stop biology. Saru asks Burnham to sever his threat ganglia so he can die peacefully. With knife in hand, she breaks down, telling him that he is her family. Saru feels the same about her – Burnham replaced the sister he left on his home planet. Saru believes if the two of them can have formed this bond then she must do the same with Spock.



Burnham prepares to amputate the ganglia, but they fall off on their own. Saru is surprised but rejuvenated. For the first time in his life, he is no longer ruled by fear, in fact, he feels his power. Realizing that his species have been governed by a lie, he wonders what this could mean for Kelpians.



Back on the bridge, the crew learns that the sphere downloaded its entire legacy into the Discovery computers. They have access to everything it has seen over the past 100,000 years including, quite fortunately, the last known course of Spock’s shuttle.



In Engineering, Tilly continues to see and hear May, but Stamets and Reno don’t believe her as they have been infected by the spores. Realizing they are both hallucinating, Stamets inoculates Reno and himself. But, when he goes to inoculate Tilly, she has disappeared. Searching the remnants of the symbiote, they realize that Tilly has been taken…but where?

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