While in unfamiliar territory, the U.S.S. Discovery crew is forced to get creative in their next efforts to survive opposing and unprecedented forces and return home.

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)
Mary Chieffo (L'Rell)
Sam Vartholomeos (Danby Connor)

Emily Coutts (Lt. Keyla Detmer)
Patrick Kwok-Choon (Lt. Gen Rhys)
Julianne Grossman (Discovery Computer)
Sara Mitich (Lt. Cmdr. Airiam)
Ali Momen (Lt. Kamran Gant)
Oyin Oladejo (Lt. Joann Owosekun)
Ronnie Rowe Jr. (Lt. Ronald Bryce)
Chris Violette (Lt. Britch Weeton)
Romaine Waite (Lt. Troy Januzzi)

• First episode of Chapter 2. It was directed by TNG alum Jonathan Frakes.
  
• The Discovery has jumped into the Mirror Universe, where the Terran Empire rules. (The Terran I.S.S. Discovery has seemingly switched places.)
  
• This episode references the U.S.S. Defiant and the Original Series episode "Mirror, Mirror" and the Enterprise episodes "In a Mirror, Darkly" and "In a Mirror, Darkly, Part II".
  
• In the mirror universe, the captain of the I.S.S. Discovery is Tilly. Burnham was captain of the I.S.S. Shenzhou — but was missing and presumed dead... killed by a fugitive Lorca after he attempted to overthrow the Emporer.
  
• Danby Connor rose to position of captain of the Shenzhou after Burnham went missing. (Ensign Connor died in the "Battle at the Binary Stars" in the prime universe.)
  
• The mirror version of Keyla Detmer appears without the cranial/optical implant she received from her injuries during the "Battle at the Binary Stars". She is the Shenzhou's first officer.
  
• In addition to Detmer and Connor, other Shenzhou bridge crew members make a return appearance: Kamron Gant, Britch Weeton, and Troy Januzzi.
  
• It appears the fan theory about Tyler being Voq is indeed true. Dr. Culber runs a deep scan on Tyler and finds that he has been physically and mentally altered by the Klingons: his body has been changed and another personality has been overlaid on top of his original. Tyler snaps Culber's neck.
  
• L'Rell recites Kahless's prayer to Tyler, which is supposed to unlock the Voq personna, but it doesn't work.