The Ghosts in the Clouds: Book 4

Mr. Snarf has been a bad ghost. He hasn't scared people. In fact, he's even made friends! Now some grumpy ghosts are taking him away from Hotel Strange. The hotel's other residents set off to rescue him, taking to the clouds in a hot air balloon in search of the Kingdom of Ghosts. Once they arrive, the ghosts put the Hotel Strange gang on trial--will they be able to save Mr. Snarf?