Captain Pike and his crew welcome a Klingon defector aboard the U.S.S. Enterprise, but his presence triggers the revelation of some shocking secrets.

Anson Mount (Captain Christopher Pike)
Ethan Peck (Lieutenant Spock)
Jess Bush (Nurse Christine Chapel)
Christina Chong (Lt. La'an Noonien-Singh)
Celia Rose Gooding (Ensign Nyota Uhura)
Melissa Navia (Lt. Erica Ortegas)
Babs Olusanmokun (Dr. Joseph M'Benga)
Rebecca Romijn (Lt. Commander Una Chin-Riley)

Robert Wisdom (Ambassador Dak'Rah)
Clint Howard (Commander Buck Martinez)

Saida Ali (Jix)
Ryan Allen (Polk)
Carolyne Das (Lead Pilot)
Rong Fu (Lt. Jenna Mitchell)
Kyle Gatehouse (Lieutenant Va'Al Trask)
Jose Gutierrez-Solana (Ensign Alvarado)
Brendan Jeffers (Ensign Inman)
Alex Kapp (U.S.S. Enterprise Computer)
Vanessa Smythe (Harper)

• Dak'Rah previously served the Klingon Empire as General Dak'Rah, where he was named the Butcher of J'Gal by the Klingons.
  
• This episode includes flashbacks to the moon of J'Gal during the Federation-Klingon war, where Chapel and M'Benga served. The Klingons massacred the civilians on Athos Colony. Dak'Rah says he defected because of the orders.
  
• M'Benga created the "Protocol 12" serum, which consists of adrenaline and painkillers.
  
• The Klingons named Dak'Rah the Butcher of J'Gal because he killed the Klingon officers who served under him and escaped. It was actually M'Benga who killed the Klingons and Rah fled like a coward, making M'Benga the actual Butcher of J'Gal.
  
• After revealing this, M'Benga kills Rah.
  
• Clint Howard (Dr. Martinez) has appeared in four other Star Trek series, starting back in 1966 with The Original Series episode "The Corbomite Maneuver".