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.

Nate the Great and his dog Sludge look for Annie's housekey which has mysteriously disappeared.

When Rosamond turns a phone message from Pip's mother into a music lesson with a secret meaning, Nate the Great steps in to solve the mystery.

"Nate the Great and his dog, Sludge, would like to take a break from detective work, but new cases--cases they do not want--await them"--

Rosamond throws a birthday party for her cousin, Lizzy, and invites Lizzy's four pet snakes, Nate, and his dog, Sludge. Nate does not like snakes, but when one goes missing, he faces his fears and puts his detective skills to work to find the missing guest.

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.

"The Earth Day Fair is days away, but Nate's classroom project--a robot named Mr. Butler--has disappeared. Nate the Great and his dog, Sludge, take on the unusual case, and they are soon searching high and low in and around the school. Will Nate find the robot in time for the fair?"--

A friendly competition to grow the best organic garden is underway. The prize is tempting--a ribbon, a photo and article in the newspaper, and some all-you-can eat favorites from Ned's Diner! Esmeralda, Annie, Oliver, and Rosamond are among the competitors. Just a few days before contest judging, some of Rosamond's tomatoes go missing, and Nate and Sludge are called to investigate. Who is eager for tomatoes, and why? Nate and Sludge are on the case...