As Nate the Great sets to work on his first international case, he searches for a lost "something" and saves the King of Sweden from a troublesome traveler.
Even a deep snow the week before Christmas can't keep Nate the Great and his dog Sludge from finding the special card sent to Annie's dog Fang by his mother.
Nate the Great and his sleuthing dog, Sludge, must become detectives and investigate the case of the missing pink piece of paper that has on it the perfect name, which Esmeralda came up with, to call Rosamond's pet concert.
While traveling on the train to San Francisco with his cousin Olivia's owl, Nate the Great and his dog Sludge must use all of their detective skills when the owl suddenly disappears.