A surprise visitor to the U.S.S. Discovery brings shocking news about Spock and dredges up past regrets for Burnham. Following the asteroid incident, Tilly struggles to keep a grip on her reality. L'Rell's authority on Qo'noS is threatened.

Burnham and the crew navigate a dangerous alien landscape in a race against time to save Tilly's life, but Stamets is not at all prepared for what they find in the process. Section 31 is assigned to help track down Spock, much to Pike's dismay.

Burnham goes to Vulcan in search of Spock, where she unearths surprising family secrets. In researching what is left of the Red Angel's signal over Kaminar, Pike and Tyler end up in battle with time itself. Georgiou has a few tricks up her sleeve for Leland and Section 31.

Spock and Burnham head to Talos IV, where the process of healing Spock forces the siblings to confront their troubled past. Stamets desperately tries to reconnect with Hugh, while Tyler struggles to shed the crew's suspicions of him due to his past as Voq.

Burnham is stunned when she learns her ties to Section 31 run deeper than she ever fathomed. Armed with the identity of the Red Angel, the U.S.S. Discovery goes to work on its most critical mission to date.

Burnham receives the reunion she's been longing for, but it doesn't go quite as she imagined. Georgiou and Tyler sense a disturbing change in Leland.

When the U.S.S. Discovery's crucial mission does not go according to plan, Burnham realizes what must ultimately be done. The crew prepares for the battle of a lifetime as Leland's Control ships get closer.

The U.S.S. Discovery battles against Control in a fight not only for their lives but for the future, with a little help from some unexpected friends. Spock and Burnham discern vital new connections between the red signals while Burnham faces one of life’s harshest truths: the right decisions are often the hardest to make.