Tilly and Adira lead a team of Starfleet Academy cadets on a training mission that takes a dangerous turn. Meanwhile, Burnham and Saru are pulled into tense negotiations on Ni'Var, and Dr. Culber helps Book deal with his grief.

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)

Ian Alexander (Gray Tal)
David Cronenberg (Dr. Kovich)
Chelah Horsdal (President Laira Rillak)
Tara Rosling (President T'Rina)
Amanda Arcuri (Cadet Val Sasha)
Seamus Patterson (Cadet Harral)
Adrian Walters (Cadet Taahz Gorev)

Avaah Blackwell (Lieutenant Ina)
Orville Cummings (Lieutenant Christopher)
David Benjamin Tomlinson (Lieutenant Linus)
Patrick Haye (Ferin)
Piotr Michael (Shuttle Computer)
Nck Name (Lieutenant Callum)

• After the negoatiations, Ni'Var votes to rejoin the Federation, making the total number of worlds 60.
  
• Tilly leaves Discovery to take a teaching position at Starfleet Academy. She won't be seen again until the season finale, "Coming Home".
  
• Kovich's role has never been fully defined, but it appears he oversees Starleet Academy to some extent.