10 Times Star Trek Hit The Reset Button
6. Star Trek Does 9/11

While Star Trek: Voyager is a fantastic show in its own right, introducing some of the most influential characters in the franchise (Captain Janeway, Seven of Nine and The Doctor among them), it didn't do an awful lot to reset the franchise. The aforementioned examples of Year of Hell and Endgame serve to reset their own stories, but not the franchise as a whole.
The same cannot be said of Enterprise. This was the first series to air after the September 11th attacks and the first season was poorly received by audiences. This was a combination of occasionally shoddy and clunky writing, mixed with a wide-eyed wonder that simply wasn't in the air at the time.
It was renewed for a second season and the writers decided to shake things up in a way that had rarely been attempted before. In the closing episode of the second season, an alien weapon arrives from nowhere and cuts a devastating swathe across Earth, killing seven million people.
It was a direct parallel to the 9/11 attacks that equally left people stunned and afraid, completely changing the tone of the show for the third season. It also led to Star Trek's longest experiment with serialised storytelling up to that point, with the third season of Enterprise effectively becoming one long film.
The quality of the show drastically improved but unfortunately the audience numbers didn't. Though it was renewed for a fourth season, it was to be its last.