Burnham and Stamets enter the mycelial network to rescue Tilly and find Hugh Culber, who is brought back to life.
Burnham and Stamets enter the mycelial network to find Tilly, who has been taken there by May to stop a monster she believes is harming its ecosystem. Discovery also tracks down the shuttle Spock fled in, only to find Georgiou of Section 31 aboard, and Captain Leland assigns Tyler as Section 31's liaison to the ship.
The monster turns out to be Hugh Culber, whose consciousness Stamets unknowingly carried into the network when Culber died. Burnham persuades May to use the cocoon to rebuild Culber's body, and he and Tilly are brought back to Discovery. Kirsten Beyer wrote the episode and David Barrett directed.