Osyraa attacks Book's home planet and the Discovery travels there to help. Stamets and Adira investigate The Burn.

Discovery ventures to the Verubin Nebula, where Burnham, Saru, and Culber make a shocking realization about the origin of the Burn. The rest of the crew faces an unexpected threat.

After capturing the U.S.S. Discovery, Osyraa seeks a meeting with Admiral Vance while Burnham and the crew must overcome unimaginable odds as they attempt to regain command of their ship.

As the Emerald Chain tightens its grip and the mystery of the Burn is finally solved, Burnham and the crew have one last chance to save themselves - and the Federation.