Star Trek: The Next Generation
Although slightly repetitive, Cause and Effect is one of the better episodes of Star Trek: The Next Generation. It starts off with the Enterprise and its whole crew being destroyed, and gets more interesting as it progresses.
It depicts a series of events happening again and again, much like in Philip K. Dick's short story A Little Something for Us Tempunauts and the films 12:01 and Groundhog Day. The crew try to find a way to stop themselves looping or being destroyed again.
I'll spare you the detailed, spoiler-filled synopsis that you can find on the back of the box and instead point out that it has a cameo appearence by Kelsey Grammer of Cheers and Frasier fame.
While not a very emotionally charged episode (if that's what you're after, you'd be better off with The Next Phase or The Inner Light), the timetravelling theme gives it a much more traditional sci-fi slant, and it's definitely one of the episodes worth watching.
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