When the Discovery crew infiltrates Section 31’s headquarters, suspicions arise that the crew may have a traitor in their midst. Burnham tries to help Spock, but her efforts don’t go as planned.

Sonequa Martin-Green (Commander Michael Burnham)
Doug Jones (Commander Saru)
Anthony Rapp (Lt. Cmdr. Paul Stamets)
Mary Wiseman (Ensign Sylvia Tilly)
Anson Mount (Captain Christopher Pike)

Jayne Brook (Admiral Katrina Cornwell)
Ethan Peck (Lieutenant Spock)
Rachael Ancheril (Commander Nhan)

Hannah Cheesman (Lt. Cmdr. Airiam)
Emily Coutts (Lt. Keyla Detmer)
Patrick Kwok-Choon (Lt. Gen Rhys)
Oyin Oladejo (Lt. Joann Owosekun)
Ronnie Rowe Jr. (Lt. Ronald Bryce)
Julianne Grossman (Discovery Computer)
Arista Arhin (Young Michael Burnham)
Alisen Down (Starfleet Psychiatrist)
Tyler Hynes (Stephen)
Tara Nicodemo (Admiral Patar)

• Admiral Cornwell tells Pike the admirals who run Section 31 haven't responded to her in weeks and she is locked out of their A.I. system, Control. She reveals Admiral Patar to be a logic extremist and has taken control of Control. She sends Discovery to Section 31 Headquarters to arrest Patar and to reset Control.
  
• Tilly deciphers the recipient of the transmissions, which is Section 31 Headquarters, a space station that was formerly a penal colony.
  
• We learn more about Airiam in this episode. She is human, and received cybernetic augmentation after a shuttle accident nearly killed her. Her new husband, Stephen, was killed in the accident. Because her memory has finite storage, she goes through her memories weekly to delete or archive them. When she goes through her memories, we see her interactions with the rest of the crew.
  
• Control infects Airiam with a virus, who has been sending the Sphere data to Control. Before Airiam can complete the transaction, she briefly regains control and begs Burnham to open the airlock door. She tells Burnham to look for "Project Daedalus" just before Nhan ejects her into space.
  
• The episode ends with Airiam's favorite memory of her and her husband walking on the beach. Instead of music playing during the closing credits, the soft sound of waves can be heard.
  
• This is the first episode written by Michelle Paradise, who will go on to serve as showrunner for Season 3.