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 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.