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.