Thanksgiving is just around the corner, but the kids in Green Lawn have more than just a big holiday feast on their minds! A mysterious new couple has just moved into the house right next door, and they are acting incredibly suspicious. Bradley, Brian, Nate, and Lucy are watching closely as the strange neighbors begin building a massive, towering wooden fence around their property. The bizarre behavior does not stop there. The neighbors are hauling in heavy crates full of strange metal parts, clearly building something massive in secret. They have even pitched a huge, shadowy tent right in the middle of their backyard, guarded perfectly by a very large and intimidating dog! The four friends are convinced that something highly unusual is going on right next to their own home. The young detectives grab their notebooks and start spying on the secret project. Follow along as they quietly gather clues and try to peek over the giant fence without getting caught by the scary guard dog. What in the world are the new neighbors hiding inside that tent? Dive into this thrilling autumn mystery and help uncover the truth!