Patrolling near the Romulan Neutral Zone, the U.S.S. Enterprise finds a ship manned by Carter Winston, a Federation citizen and philanthropist who has been missing for five years.

William Shatner (Captain James T. Kirk)
Leonard Nimoy (Commander Spock)
DeForest Kelley (Dr. Leonard H. McCoy)

George Takei (Lt. Hikaru Sulu)
Nichelle Nichols (Lt. Anne Nored)
Majel Barrett (Nurse Christine Chapel)
James Doohan (Lt. Cmdr. Montgomery Scott)
Ted Knight (Carter Wilson)

• This episode introduces comm officer Lieutenant M'Ress (voiced by Majel Barrett) and the feline-like Caitian species.
  
• Lt. Uhura doesn't appear in this episode, but Nichelle Nichols voices Lt. Anne Nored, fiancée of Carter Winston.