The U.S.S. Discovery is tasked with a high priority mission to planet Pahvo to learn the science behind the Klingon's cloaking technology. Meanwhile, L'Rell interrogates Admiral Cornwell.

Sonequa Martin-Green (Specialist Michael Burnham)
Doug Jones (Commander Saru)
Shazad Latif (Lt. Ash Tyler)
Anthony Rapp (Lt. Paul Stamets)
Mary Wiseman (Cadet Sylvia Tilly)
Jason Isaacs (Captain Gabriel Lorca)

Jayne Brook (Admiral Katrina Cornwell)
Mary Chieffo (L'Rell)
Wilson Cruz (Dr. Hugh Culber)
Kenneth Mitchell (General Kol)

Michael Boisvert (Captain Kovil)
Conrad Coates (Admiral Terral)
Emily Coutts (Lt. Keyla Detmer)
Anthony Grant (Klingon Communications Officer)
Julianne Grossman (Discovery Computer)
Patrick Kwok-Choon (Lt. Gen Rhys)
Sara Mitich (Lt. Cmdr. Airiam)
Oyin Oladejo (Lt. Joann Owosekun)
Ronnie Rowe Jr. (Lt. Ronald Bryce)
Tyler Evan Webb (Klingon Guard)

• "Si Vis Pacem, Para Bellum" is Latin for "If you want peace, prepare for war."
  
• Like the previous episode, this episode does not contain an opening act. It goes directly from the Previously on Star Trek: Discovery sequence into the title sequence.
  
• The episode opens with the U.S.S. Discovery coming to the aid of the U.S.S. Gagarin NCC-1309 (Shepard-class), commanded by Captain Kovil. It is ultimately destroyed by the cloaking Klingon ships, as were the U.S.S. Hoover and U.S.S. Muroc in separate ambushes.
  
• L'Rell requests asylum from Admiral Cornwell. If L'Rell helps her escape, she will in return help the Federation defeat General Kol. When they are caught en route to L'Rell's shuttle, L'Rell appears to kill Cornwell in a fight, and drags her to the brig, where she finds the bodies of T'Kuvma's followers.
  
• General Kol asks for L'Rell's allegiance to House Kor. Though she appears to give it, he sees through her lies and has her taken away.