Burnham studies the creature from the Glenn and realizes it can guide the spore drive, letting Discovery rescue the besieged colony Corvan II.
Lorca puts Burnham to work on the creature recovered from the USS Glenn, hoping it can be turned into a weapon. Security chief Commander Landry is killed when she tries to sedate the giant tardigrade-like animal, but Burnham becomes convinced it is not simply a predator.
The Klingons are attacking the dilithium colony of Corvan II, and an unstable spore jump nearly sends Discovery into a star. Burnham and Paul Stamets work out that the creature, which Burnham names Ripper, can navigate the mycelial network. Once it is linked to the drive in Engineering, Discovery reaches Corvan II and drives the Klingons off. Meanwhile Kol takes over T'Kuvma's followers and abandons Voq, and L'Rell offers Voq her help. Olatunde Osunsanmi directed from a script by Jesse Alexander and Aron Eli Coleite.