All aboard the Owl Express! Nate, the great detective, and his dog Sludge, hit the rails on their latest case. Their mission: To guard an owl named Hoot. Hoot belongs to Nate's cousin, Olivia Sharp, and she thinks someone on the train might be out to get her feathered friend. But "whooo?" Sludge keeps an eye on the owl's cage while Nate snoops for clues. Then Hoot disappears! With many suspects to question, and many places to look, Nate knows one thing for sure--being the bodyguard to a little bird is a lot more work than he ever imagined! As the train races toward its final stop, can Nate sort out the mystery of the vanishing owl?