Burnham and the U.S.S. Discovery crew travel to Book’s home planet of Kwejian to help rescue it from Osyraa, the formidable leader of the Emerald Chain. Meanwhile, Stamets and Adira continue their search for valuable information on the origin of the Burn.

Sonequa Martin-Green (Commander Michael Burnham)
Doug Jones (Captain Saru)
Anthony Rapp (Lt. Cmdr. Paul Stamets)
Mary Wiseman (Ensign Sylvia Tilly)
Wilson Cruz (Dr. Hugh Culber)
David Ajala (Cleveland Booker)

Michelle Yeoh (Philippa Georgiou)

Oded Fehr (Admiral Charles Vance)
Noah Averbach-Katz (Ryn)
Blu del Barrio (Adira Tal)
Ache Hernandez (Kyheem)
Janet Kidder (Osyraa)
Ian Lake (Tolor)

Emily Coutts (Lt. Keyla Detmer)
Patrick Kwok-Choon (Lt. Gen Rhys)
Oyin Oladejo (Lt. Joann Owosekun)
Ronnie Rowe Jr. (Lt. Ronald Bryce)
Sara Mitich (Lt. Nilsson)
Ross Carter (Lt. Haj)
Raven Dauda (Dr. Tracy Pollard)
Luca Doulgeris (Leto)
Fabio Tassone (Book's ship computer)
David Benjamin Tomlinson (Lt. Linus)
Jhaleil Swaby (San)

• This episode introduces Osyraa, the main antagonist for Season 3.
  
• Stamets and Adira determine the Burn's origin is the Verubin Nebula.
  
• Adira confides in Stamets they want to be referred to with a gender neutral pronoun "they", and sometimes feels like the personalities of the other Trill hosts are taking over.
  
• Osyraa feeds her nephew Tolor to a trance worm for letting Ryn escape. She wants Ryn because he knows the Emerald Chain is running out of dilithium.