Captain Sisko and the crew travel back in time to a pivotal moment in the history of the original Starship Enterprise. The U.S.S. Defiant is returning from Cardassian space with the Bajoran Orb of Time. A Klingon named Arne Darvin, surgically altered to look human, has come aboard as a passenger. He uses the Orb to send the U.S.S. Defiant more than one hundred years into the past — near the original U.S.S. Enterprise NCC-1701 as it orbited Deep Space Station K-7. Records reveal Darvin was a spy then, and that he was caught having poisoned a shipment of grain on the station. Darvin is out to change history, possibly by killing Captain James T. Kirk, who originally exposed him as the spy.

Jack Blessing (Dulmur)
James W. Jansen (Lucsly)
Charlie Brill (Arne Darvin)
Leslie Ackerman (Waitress)
Charles S. Chun (Engineer)
Deirdre L. Imershein (Lt. Watley)

• This episode, along with Voyager's "Flashback", celebrates Star Trek's 30th anniversary.
  
• This fun episode uses Forrest Gump-type techniques to seamlessly integrate the DS9 cast into the original Star Trek episode, "The Trouble With Tribbles".
  
• One of the Temporal Investigators states to Sisko, "Be more specific. There have been 5 starships with the name Enterprise." The other corrects him, "Six." (This is noteworthy because this episode happens before Star Trek First Contact, which begins on stardate 50893.5. This episode occurs sometime between stardates 50000-50200.)
  
• The difference in appearance between the original series Klingons is noted here, though Worf dismisses the conversation as something that is not discussed. It will be formally addressed in the Star Trek: Enterprise episodes "Affliction" and "Divergence".