U.S.S. Voyager comes to the aid of an alien, Steth, who claims to be the test pilot of a new spacecraft that has run into trouble. Paris, who has become weary of being on the U.S.S. Voyager, volunteers to help him repair his ship. However, Steth is able to copy Paris's DNA and swaps physical appearances with him. Paris is then left behind in Steth's ship while the imposter takes over his duties at the helm and leaves the real Paris behind. It isn't long before "Steth" is confronted by Daelen, another alien who is seeking her original form. Back on the U.S.S. Voyager, Janeway suspects something is wrong, but Steth assumes her appearance and takes command.
