Osyraa uses Discovery to approach Federation headquarters and offers Vance a treaty, while Burnham fights to retake her ship from inside.
Osyraa disguises her flagship as an attacker chasing Discovery so that Vance lets Discovery inside the shields of Federation headquarters. Burnham and Book reach headquarters through a transwarp tunnel, but Zareh captures Book. Osyraa's scientist Aurellio questions Stamets about the spore drive, and the bridge crew is held hostage.
Osyraa offers Vance a treaty uniting the Federation and the Emerald Chain, but he insists she must stand trial, and she leaves the talks. The bridge crew breaks free with help from Ryn and Book. Burnham frees Stamets and sends him off the ship to keep the drive from Osyraa, who then kills Ryn. The title comes from Julius Caesar. Kenneth Lin wrote the episode and Jonathan Frakes directed.