...So where are they GOING? Not to home, since the missing posters. And she's not carrying the mold with her to infest other places/people. She seems happy enough to go with the people in the van. Which is odd.
I read it as Mind-Control/Transformation recruitment site for underground slave trade, maybe even specify that want female realators/renovators/electricians or whatever when get people sent to the house. Long vacancy probably also lends itself to some college-shenanigans like dares to break into the old house. That's my interpretation anyway, and I'm happy with it.
