The Prodigal Son
S01E16 - Airdate: 1989-02-06
Runtime: 60 min
Harrison is kidnapped by a unique modern artist named "Quinn", who's actually one of the aliens being hunted by his kind. He's mysteriously immune to Earth's bacteria, so the other aliens want to learn his secret through dissection. Quinn wants to set up a dialogue with Earth's leaders to arrange a "peaceful" takeover of the planet as opposed to an all-out slaughter of humanity.
Episode details and rating from TVmaze.