Captain Burnham and the U.S.S. Discovery race to stop Book and Ruon Tarka from launching a rogue plan that could inadvertently endanger the galaxy.

Sonequa Martin-Green (Captain Michael Burnham)
Doug Jones (Captain Saru)
Anthony Rapp (Lt. Cmdr. Paul Stamets)
Wilson Cruz (Dr. Hugh Culber)
David Ajala (Cleveland Booker)

Oded Fehr (Admiral Charles Vance)
Rachael Ancheril (Commander D. Nhan)
Shawn Doyle (Dr. Ruon Tarka)
Tara Rosling (President T'Rina)
Annabelle Wallis (Zora)

Emily Coutts (Lt. Cmdr. Keyla Detmer)
Patrick Kwok-Choon (Lt. Cmdr. Gen Rhys)
Oyin Oladejo (Lt. Cmdr. Joann Owosekun)
Ronnie Rowe Jr. (Lt. Cmdr. Ronald Bryce)
Sara Mitich (Lt. Cmdr. Nilsson)
Orville Cummings (Lieutenant Christopher)
David Benjamin Tomlinson (Lieutenant Linus)
Piotr Michael (Shuttle Computer)
Fabio Tassone (Book's Ship Computer)

• Rachael Ancheril (Nhan) makes her first appearance since last season's "Die Trying". She is now a member of Federation Security, and was assigned to assist Discovery in stopping Booker and Tarka, in case the crew hesistates in doing what needs to be done.
  
• Book agrees to stand down, but Tarka launches his isolytic weapon regardless. It destroys the DMA, however a new DMA appears in its place.
  
• Tarka's motive for destroying the DMA is he wants the power source… which is on the other side of the wormhole.
  
• Mary Wiseman (Sylvia Tilly) and Blu del Barrio (Adira Tal) do not appear in this episode, and their names do not appear in the opening credits.