Where's My Kid?

We live at the top of a hill on a cul-de-sac. There are no neighbors to one side of us, and no neighbors behind us. It's a nice quiet area of the neighborhood and great place for the kids to run around and play. Ryan has a nice friend who lives two houses away, and they get along really well. They both have active imaginations and come up with great things to do. A few days before the Christmas break, Ryan asked me and the kids and my friend Megan and her kids who were visiting to come see the tree fort he and his friend had been building. We took a hike back behind our house and down into a ravine. There they had been rebuilding a tree fort that some "teenagers" had built and taken down. I had no idea what they had been up to!