A time rift brings the U.S.S. Enterprise NCC-1701-C 22 years into the future, thereby changing events: Lt. Tasha Yar has returned and the Federation is now at war with the Klingons — and losing. Guinan senses that something is wrong and convinces Picard that the Enterprise-C must return to repair the timeline. Knowing that she dies a senseless death in the proper timeline, Yar decides to go back in time with the Enterprise-C.

Whoopi Goldberg (Guinan)
Denise Crosby (Lt. Tasha Yar)
Christopher McDonald (Lt. Richard Castille)
Tricia O'Neil (Captain Rachel Garrett)

• The Enterprise-C was destroyed helping to defend Klingon outpost on Narendra III from a Romulan attack.
  
• When the Enterprise-C appears, Worf and Troi disappear from the bridge and Lt. Tasha Yar appears in Worf's place. Wesley Crusher wears a Starfleet uniform with rank of ensign. All officers carry phasers as standard issue.
  
• The captain's log begins with "Military log, Combat Date..." instead of "Captain's log, Stardate..." The warship (not starship) Enterprise-D is capable of transporting over 6,000 troops.
  
• Guinan is very insistant that Picard restore the timeline, but does not protest when Picard allows Tasha to transfer to the Enterprise-C (though she may not have known he did this at the time).
  
• This episode sets up Denise Crosby's return as Commander Sela in "Redemption, Part I".
  
• Guinan gives Worf his first taste of prune juice ("A Warrior's Drink™"). It becomes his drink of choice throughout the series and on DS9.
  
• Troi has no speaking lines in this episode.
  
• Dr. Selar is heard being paged to sickbay. (See "The Schizoid Man".)