While Captain Burnham leads an away mission to a planet that was once home to the aliens responsible for the DMA, Book and Tarka secretly infiltrate the U.S.S. Discovery.

Sonequa Martin-Green (Captain Michael Burnham)
Doug Jones (Captain Saru)
Anthony Rapp (Lt. Cmdr. Paul Stamets)
Wilson Cruz (Dr. Hugh Culber)
Blu del Barrio (Ensign Adira Tal)
Tig Notaro (Commander Jett Reno)
David Ajala (Cleveland Booker)

Shawn Doyle (Dr. Ruon Tarka)
Chelah Horsdal (President Laira Rillak)
Tara Rosling (President T'Rina)
Hiro Kanagawa (Dr. Hirai)
Phumzile Sitole (General Ndoye)

Emily Coutts (Lt. Cmdr. Keyla Detmer)
Patrick Kwok-Choon (Lt. Cmdr. Gen Rhys)
Oyin Oladejo (Lt. Cmdr. Joann Owosekun)
Sara Mitich (Lt. Cmdr. Nilsson)
Raven Dauda (Cmdr. Tracy Pollard, MD)
David Benjamin Tomlinson (Lieutenant Linus)
Calyx Passailaigue (Engineer #1)
Jas Dhanda (Engineer #2)
Piotr Michael (Shuttle Computer)

• While on Discovery, Book persuades General Ndoye to secretly help Tarka.
  
• When Tarka is caught by Reno, he takes her hostage.
  
• Mary Wiseman (Sylvia Tilly) does not appear in this episode and her name does not appear in the opening credits.
  
• This episode debuted simultaneously with the Picard episode "The Star Gazer".