In the mirror past, Georgiou tries to spare Burnham's counterpart and save Saru's, before Carl reveals himself as the Guardian of Forever.
Back in the Terran Empire, Georgiou tries to build a better empire with her own Burnham beside her, persuades the mirror Saru that vahar'ai is a natural change rather than a reason to cull Kelpiens, and spares him. The mirror Burnham turns against her anyway, ending in a violent confrontation between them.
Carl reveals that he is the Guardian of Forever, the time portal from the original series, and that the experience was a test of character. He sends Georgiou on to a time and place where she can survive, and Burnham returns to Discovery. Chloe Domont directed.