Instagram-famous triplets Cecily, Amber, and Rudy -- the children of home renovation superstars -- are ready for a perfect summer ... they've just moved into the site of their parents' latest renovation: a multi-million dollar McMansion in upstate New York -- when they begin to receive chilling messages from someone calling themselves The Follower. And it becomes clear that this anonymous threat is more than a simple Internet troll, and can't wait...