Star Trek: Enterprise: Season 3, Episode 8

3 - 8: Twilight

After an accident on the Enterprise in 2153, a spatial distortion leaves Archer with a puzzling form of amnesia due to interspatial parasites and unable to form new long-term memories. He wakes up every day not remembering anything from the day before. At one point, he is further confused about finding himself in the future aboard an Enterprise commanded by T'Pol. Twelve years into the future, he wakes up one morning and is stunned to learn the outcome of the human-Xindi conflict. After destroying Earth, the Xindi continued searching the galaxy, determined to annihilate all Humans. The remnants of humanity have settled on the distant planet Ceti Alpha V. Now, Archer learns that he may be the key to undoing this entire tragedy if Phlox's new treatment destroys the parasites without harming him.