Caught by Starfleet and facing court martial, paranoia grows as Picard struggles to uncover whether a prodigal crewman from his past has returned as an ally — or an enemy hellbent on destroying them all.

Patrick Stewart (Admiral Jean-Luc Picard)
Jeri Ryan (Commander Seven of Nine)
Michelle Hurd (Commander Raffi Musiker)
Ed Speleers (Jack Crusher)

Michael Dorn (Captain Worf)
Michelle Forbes (Commander Ro Laren)
Jonathan Frakes (Captain William T. Riker)
Gates McFadden (Dr. Beverly Crusher)

Todd Stashwick (Captain Liam Shaw)
Ashlei Sharpe Chestnut (Ensign Sidney La Forge)
Kirk Acevedo (Krinn)

Stephanie Czajkowski (Lieutenant T'Veen)
Amy Earhart (U.S.S. Titan Computer)
Joseph Lee (Lt. Matthew Arliss Mura)
Grace Lee (La Sirena Computer)
Jin Maley (Ensign Kova Rin Esmar)
Tiffany Shepis (Dr. Ohk)
Hope Brown (Transport Officer)
Justin Dobies (Bridge Security Officer)
Alessandro Garcia (Intrepid Security Officer #1)
William Greenberg (Male Changeling Ensign)
John Pope (Young Ensign)
Tarina Pouncy (Intrepid Security Officer #2)

• Commander Ro Laren arrives via the U.S.S. Intrepid NCC-79520 to question Picard and Riker.
  
• Picard and Ro are both angry and hurt over the events of "Preemptive Strike", which took place about 30 years prior. They use this to determine neither is a changeling. She reveals to Picard the changeling infiltration has gone up to the highest levels of Starfleet.
  
• Dr. Crusher and Dr. Ohk examine the changeling body, noting that it did not revert to liquid form upon death (remaining in Ensign La Forge's shape). It is also able to replicate internal organs and blood. The body contains no DNA, but it's enough to fool the biosensors.
  
• Ro was sent to prison after her time with the Maquis, and then was recruited by Starfleet Intelligence. She is revealed to be Worf's handler.
  
• Jack is having visions of a red door and red tendrils, with Beverly's voice whispering "find her". They seem to be increasing in intensity.