The disappearance of the tall man in the high hat

the long version

"The third in the Alex and Ms. Mulholland series, finds our detectives growing and changing. Alex has turned 13 and, Ms. M observes, "eccentric." Tasha Mulholland, to his chagrin, almost finds romance. When the tall man in the top hat disappears at the door of the Museum, things start happening to its historic objects that puzzle everyone. And when the tall man's wicked wife meets an untimely death, the search for him grows more intense. While the ghosts who haunt the Museum and the countryside almost turn the detectives' world upside down, it's still the living who do it the most harm."--Author's website.