The Glass Playground. The Hollow Archive, #5

Nine years ago, a six-year-old boy vanished inside Glasshouse Playland. Now its dead cameras are recording again. Owen Merritt was seventeen when Theo Kline disappeared during a birthday party-and the town never stopped wondering what he failed to see. Then a video appears online, filmed inside the abandoned play center from a camera that should have no power. Children move through the dark tunnels.
The ball pit shifts on its own. Near the mirrored maze stands Theo, still six years old and wearing the same yellow rocket shirt from the day he vanished. Across the glass, four words appear:YOU LEFT ME WAITING. As old cameras awaken and children begin appearing in reflections across town, Owen is forced back toward the place he has spent nine years trying to escape. With Theo's mother and a former employee who remembers more than she has admitted, he must uncover what Glasshouse kept after everyone else stopped looking.
Because the building does not merely remember abandoned children. It knows which adults left them behind. The Glass Playground is Book Five in The Hollow Archive, a connected supernatural horror series about impossible places, buried guilt, and memories that refuse to stay dead.