Set approximately half way between the STAR TREK:  The Original Series and STAR TREK:  The Next Generation, STAR TREK: The Lost Generation begins with Captain Renalt and his crew in command of the USS ENTERPRISE, NCC 1701-B. Soon after he gained command, the ENTERPRISE was destroyed when the Federation was overthrown by an alien race called the Zaron Empire. They continued to call themselves "The Federation." The member worlds, not directly enslaved by the Zarons banded together and created the Rebellion Alliance of Planets.

However, after several missions together (included the destruction of the Zaron's, the re-formation of the United Federation of Planets, the launch of USS ENTERPRISE, 1701-D, the death of Norra, Collek, and Nimmon and a host of others) the crew of the USS ENTERPRISE find out they have been tricked by the "Sun Alien" now calling himself "Q."  Q tells the crew that he has been testing them.  What seemed like an entire lifetime (some 80 years) spanned a mere 2 hours.  Time was rolled back for the crew.  People, friends, and crew members Captain Renalt thought he knew did not even exist.  His promotion to Admiral never happened.  The virus that destroyed the Zaron Federation in Q's timeline didn't exist.  The Zaron's still controlled the Alpha Quadrant.