As the crew continues their guise, Burnham goes a merciless mission in hopes of helping the U.S.S. Discovery return home. Tilly works on restoring Stamets' neurofunction.

Sonequa Martin-Green (Specialist Michael Burnham)
Doug Jones (Commander Saru)
Shazad Latif (Lt. Ash Tyler)
Anthony Rapp (Lt. Paul Stamets)
Mary Wiseman (Cadet Sylvia Tilly)
Jason Isaacs (Captain Gabriel Lorca)

Wilson Cruz (Dr. Hugh Culber)
James Frain (Ambassador Sarek)
Michelle Yeoh (Captain Philippa Georgiou)

Emily Coutts (Lt. Keyla Detmer)
Riley Gilchrist (Shukar)
Julianne Grossman (Discovery Computer)
Devon MacDonald (Service Engineer)
Ali Momen (Lt. Kamran Gant)
Dwain Murphy (Captain Maddox)
Tasia Valenza (Shenzhou Computer)
Chris Violette (Lt. Britch Weeton)
Romaine Waite (Lt. Troy Januzzi)

• The mirror universe version of the Klingon Voq (aka the "Fire Wolf") leads a coalition of rebel species, including Klingons, Andorians, Tellarites, and Vulcans. Among them is the "Prophet," Sarek.
  
• Stamets becomes trapped in the mycelial network, where he meets his mirror self.
  
• Lt. Tyler's memories come back when he comes face-to-face with the mirror version of himself (Voq). He reveals himself to Burnham and he is taken into custody by the Discovery crew at the end of the episode. Burnham hides the Defiant data on Tyler.
  
• The Terran Emperor is revealed to be Philippa Georgiou.