Struck down by a mystery illness which has left him bedbound for much of the time, Lloyd returns to the farmhouse in Wales where he was brought up by his Aunt Mona after his parents were killed in a car crash. Other occupants of The Noddfa (Sanctuary) include fifteen-year old Alex, the wayward son of his cousin, and Mona's demented Great Uncle Stanley. Lloyd's mind turns to a mystery of his childhood - the room-sized space on the first floor of the house which has no door or window. Alex acts as his detective and they explore it with the help of a webcam. They find letters which reveal that the crash which killed his parents may not be as straightforward as it seems. Lloyd now has three mysteries to solve - his illness, the car crash, and the real purpose of The Missing Room.