Episode 8 opens with the USS Gagarin under heavy attack, and the Discovery dropping out of the sky like an avenging angel. The Discovery crew does their best, but the Gagarin is ultimately destroyed by a Klingon torpedo. Thanks to the newly rediscovered Klingon cloaking technology we all know and love, the Gagarin is the third ship to be decimated in this region of space in a short amount of time. Stamets, dazed and just a bit confused, steps out of the spore chamber and calls Tilly "Captain." Whether that is a glimpse into the future by Stamets, or just him being severely out of it remains to be seen.
Burnham, Tyler, and Saru are beamed down to Pahvo, an uninhabited planet with unique vibrational frequencies that they hope to use to combat the Klingon cloaking tech. While hiking through the forest, they encounter an entity comparable to the will-o'-the-wisp from Disney’s Brave. The beings of light urge them on to a different path, and Saru has them follow it, even as it led them away from their destination.
Saru figures out how to communicate with the beings of light and discovers that they are at least passingly sentient, which means that they cannot continue their mission until first contact protocols have been completed. Meanwhile, the Klingons are at it again. L'Rell, captain of a prison ship, wants to align herself with Kol, who rediscovered the cloaking tech. He proclaims not to trust her, as she was a T'Kuvma loyalist. Kol demands she proves herself, and she asks to be brought to the prisoner they have failed to break. L'Rell is brought to Admiral Cornwall, whom she fake-tortures so that they may chat.
Back on Pahvu, Tyler and Burnham discuss the future. Tyler dreams of his house by the lake and freshly grilled trout. Michael reminds him that all she has to look forward to is prison. Tyler suggests that they botch the mission and remain at war indefinitely. Michael disagrees, as the needs of the many outweigh the needs of the few, or the one.
At lunch on the Discovery, Tilly approaches Stamets with her concerns. He tells her about his untethered position in the time stream, and confides that he can’t tell his boyfriend about it, because then Culber would be ethically if not legally compelled to report Stamets's condition to Starfleet. They agree to quietly monitor his condition.
The beings of light on Pahvu turn out to be the generalized spirit of the planet itself. It just wants friends, someone to share existence with. Saru learns all of this and more from the spirit, and the next morning, he attempts to strand them on the planet.
Tyler tells Burnham that they have to finish their mission, with or without Saru. She wonders if doing so will violate first contact protocols, but he assures her that their hosts already gave them free reign to do as they will. L'Rell tells the Admiral about her plans to defect to the Federation. They make their escape attempt and it goes well until they’re spotted, at which point L'Rell beats and seemingly kills Cornwell. L'Rell drags the Admiral's possibly lifeless body back to her ship, where she learns that her entire crew has been killed by Kol and his followers. She vows vengeance, and goes to Kol.
Saru and Burnham fight at the base of the crystal tower/signal magnifier. The Pahvans bring Tyler to their location and together they ask the Pahvans to help them with their cause, even while Saru begs them to remain neutral and save themselves. The Pahvans decide to help the Federation, and the three are beamed back to the Discovery. In sickbay, Saru tells Michael that their time on Pahvu was the only time in his entire life he didn't feel fear.
L'Rell swears her loyalty to Kol and seconds before he has her dragged away and tortured as a traitor, they receive a transmission from the Pahvans with directions to Pahvo. In a twist, it's revealed that the Pahvans plan was to invite the Klingons over and mediate for the two enemies. Michael reminds Lorca that they are the only line of defense for the Pahvans and must remain to defend them.
Up next week: The series finale! We'll see if Michael can continue batting 1000 at killing Klingon leaders.