I'm looking for a specific J2 story that I never got to finish reading, this is what I can remember:

Jensen lives in a community where there are boundaries and a curfew because, unbeknownst to the young people, there's a pact with an alien race that they can take any unmarried young adult (one or two days a year I think) who's outside after dark. Jensen wanders past the boundary seeking out plants to study and can't get inside and is taken by Jared, and then there's him growing plants and rebelling and adapting as they travel to Jared's planet.

Found: The Journey 'verse by spn_j2fan