Paris becomes entangled with an alien who swaps bodies.
Tom Paris is restless and bored, spending his time fixing a 1969 Camaro on the holodeck and ignoring B'Elanna Torres and his work in sickbay. He perks up when Voyager helps Steth, a test pilot whose ship uses an experimental coaxial warp drive, and the two quickly become friends. Then Steth swaps bodies with him and sends him away in the alien ship.
The impostor, who knows little of Paris's life, flatters the Doctor and woos Torres, but his strange behaviour soon draws suspicion. Paris wakes in Steth's body and learns that the real Steth was also a victim of the same body-swapping alien. When the impostor is confined, it takes over Janeway and flees in a shuttle, but Paris and the real Steth catch up and capture it. Everyone is restored to their own bodies. The fourth-season episode explores Paris's restlessness, and it ends with him going to make peace with Torres.