While on a routine mission, the U.S.S. Enterprise discovers a bizarre rift in space, which reveals an unidentified vessel. Both ships are now on an alternate time line where the Federation is in the midst of a bloody war with the Klingons. The crew identifies the mysterious vessel as their ships' immediate predecessor, the U.S.S. Enterprise 1701-C, believed to have been destroyed in battle over 20 years ago. Their own crew now includes Tasha Yar, the ex-security chief who was killed in the line of duty. Meeting with the captain of that vessel, Picard learns that it was responding to a distress signal on a Klingon outpost when it was attacked by four Romulan Warbirds. But in the middle of the assault, the ship broke through the space rift, thus saving it from the destruction recorded in the history books. Although Picard and his crew are baffled by the strange appearance of the U.S.S. Enterprise-C, Guinan's alien instincts lead her to believe that the Federation's current war with the Klingons is the result of the U.S.S. Enterprise-C's presence in their future.
