Aboard the Imperial flagship Charon, Burnham is unmasked to Emperor Georgiou and realizes Lorca has come from the mirror universe all along.
Burnham and Lorca are summoned to the Charon, the Emperor's flagship. Georgiou sends Lorca to an agony booth and dines with Burnham, who saves herself by confessing that she comes from another universe. In the mycelial network, Stamets meets his mirror counterpart and an image of Culber, and learns that mirror Stamets's experiments have been poisoning the network.
From Georgiou, Burnham learns that her mirror self had conspired with the Terran Lorca in a failed coup, and she realizes that Discovery's captain is that Lorca, who has steered events to get back home. Lorca escapes the agony booth. The title comes from Macbeth. Jordon Nardino wrote the episode and Hanelle M. Culpepper directed.