On Trill, Captain Burnham, Book, and Culber must pass a dangerous test to prove themselves worthy of the next clue. Adira reconnects with Gray, and Saru's first day as ambassador is complicated by his engagement to T'Rina.

Sonequa Martin-Green (Captain Michael Burnham)
Doug Jones (Ambassador Saru)
Anthony Rapp (Lt. Cmdr. Paul Stamets)
Mary Wiseman (Lieutenant Sylvia Tilly)
Wilson Cruz (Dr. Hugh Culber)
Blu del Barrio (Ensign Adira Tal)
Callum Keith Rennie (Commander Rayner)
Tig Notaro (Cmdr. Jett Reno)
David Ajala (Cleveland Booker)

Annabelle Wallis (Zora)
Tara Rosling (President T'Rina)
Eve Harlow (Moll)
Ian Alexander (Gray Tal)

Patrick Kwok-Choon (Lt. Cmdr. Gen Rhys)
Orville Cummings (Lieutenant Christopher)
David Benjamin Tomlinson (Lieutenant Linus)
Victoria Sawal (Lieutenant Naya)
Natalie Liconti (Lieutenant Gallo)
Christina Dixon (Lt. Cmdr. Asha)
Raven Dauda (Dr. Tracy Pollard)
Andreas Apergis (Guardian Xi)
Clare Coulter (Kalzara Bix)
Ingrid Rae Doucet (Moderator)
Glen Michael Grant (Delegate)
Victor Andrés Trelles Turgeon (Duvin)

• Jinaal Bix is a joined trill who was on the Federation team that studied the progenators after their discovery in the episode "The Chase" 800 years ago.
  
• Rayner joins the crew of U.S.S. Discovery as first officer, with a demotion to rank of Commander.
  
• While she is away, Burnham tells Rayner to get to know the crew. He is obsessed with finding Moll and L'ak and can't be bothered, so he gives each crew member 30 seconds and 20 words…
  
• Guardian Xi initiates the zhian'tara ritual on Kalzara Bix to transfer Jinaal Bix's consciousness into Culber. The ritual was first seen in the DS9 episode "Facets".
  
• Duvin warns Saru that his marriage to T'Rina could hurt her political career with the Vulcan purists.
  
• After being separated for months, Adira and Gray end their relationship.
  
• Lt. Cmdr. Nilsson has apparently left U.S.S. Discovery for a post on U.S.S. Voyager.