The book “Watership Down” comes to mind. Spinning a theory here: a few colonists get snatched now and then by Topsiders doing scientific research, possibly wanting to be able to live without the suits and without mutating. The colony leaders are aware of this and cooperate secretly with the Topsiders instructions in return for “safety”.
Chic is more savvy than the other kids give him credit for. He recognizes the threat even when they don’t… yet.