After answering a distress signal from the U.S.S. Enterprise, the U.S.S. Discovery welcomes aboard Captain Christopher Pike and begins a new mission to investigate the meaning behind seven mysterious red signals. Michael Burnham grapples with her past growing up on Vulcan with her foster parents and brother Spock.

A new signal appears, prompting Stamets' emotional return to the mycelial network and leading Burnham, Pike and Owosekun to a pre-warp planet, where they face a complex ethical dilemma. Tilly's overeagerness lands her in trouble but when the planet - and Discovery's landing party - are threatened, her curiosity may be the one thing that can save them.

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.

A mysterious sphere threatens the U.S.S. Discovery even as May, in her original form, implements a plan that puts Tilly's life in danger. Saru and Burnham's bond grows when Saru is forced to acknowledge a deeply unsettling Kelpien truth. Pike receives new intel on Spock from a loyal friend.

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.

When a new signal appears over Saru's home planet, Burnham, Saru and the crew embark on a perilous mission that puts Saru in danger and raises questions about the Red Angel's intentions. Hugh struggles to come to terms with his new reality.

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.

When the Discovery crew infiltrates Section 31's headquarters, suspicions arise that the crew may have a traitor in their midst. Burnham tries to help Spock but her efforts don't go as planned.

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.

A fourth signal leads the U.S.S. Discovery to a world where Pike is forced to make a life-changing choice. Burnham and Spock investigate a Section 31 ship gone rogue, leading to a discovery with catastrophic consequences.

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.