Avoiding the storyline in Strangerville - Looking for advice and answers (No spoilers)

I had a possessed sim wandering outside a restaurant in Willow Creek last night. I only just got the pack about a week ago and this sim hasn't stepped foot in Strangerville yet. I wasn't expecting to see possessed ones in other towns, although I have seen the Scientists, Conspiracy Theorists, etc at venues in other towns. I just wasn't expecting to bump into possessed ones in a save where I haven't visited that town at all yet. It was one of the Strangerville pre-mades.