Star Trek: Voyager: Season 5, Episode 18

5 - 18: Course: Oblivion

Stardate: 52586.3 After Paris and Torres wed, the ship and its crew start to disintegrate on the molecular level due to subspace radiation caused by their new enhanced warp drive. As Voyager crew members begin dying, they make a startling discovery about their true identities. They are not the real Voyager. Every member of the crew and even Voyager itself are biomimetic duplicates from the "Demon class" planet visited months ago in the episode "Demon" (S04E24).