Burnham and Tilly join forces with the Qowat Milat to hunt the killer of a Starfleet officer, as Stamets and the science team race against the clock to prevent the dark matter anomaly from klling anyone else. Meanwhile, Adira and Gray use the zhian'tara rite to incorporate Gray's consciousness into his new synthetic body.

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

Oded Fehr (Admiral Charles Vance)
Ian Alexander (Gray Tal)
Chelah Horsdal (President Laira Rillak)
Ayesha Mansur Gonsalves (J'Vini)
Tara Rosling (President T'Rina)
Sonja Sohn (Gabrielle Burnham)

Emily Coutts (Lt. Cmdr. Keyla Detmer)
Ronnie Rowe Jr. (Lt. Cmdr. Ronald Bryce)
David Benjamin Tomlinson (Lieutenant Linus)
Khalil Abdul-Malik (Commander Patrick Fickett)
Andreas Apergis (Guardian Xi)
Mimi Côté (Qowat Milat Nun)
Luca Doulgeris (Leto)
Ache Hernandez (Kyheem)
Giovanni Spina (Provost Sta'Kiar)

• President Rillak allows Burnham to work with her mother and the Qowat Milat as a political move to keep peace with Ni'Var, who is in early talks to rejoin the Federation.
  
• The Trill rite of zhian'tara was introduced in the Deep Space Nine episode "Facets".
  
• T'Rina uses a mind meld on Book to search his memory to look for traces of tachyons when the dark matter anomaly (DMA) destroyed Kwejian. She doesn't find any evidence of tachyons, but does help Book relive the details of his last memory of Leto and Kyheem.
  
• Khalil Abdul-Malik is credited as "Credence First Officer," but he is named in the episode as Patrick Fickett.