Nate, the great detective, and his dog, Sludge, are off to San Francisco! They're going to visit Nate's cousin Olivia Sharp. She's a detective, too, and a very busy one.Olivia isn't around to solve her case number 22. Her client, Duncan, has lost his joke book. He tells Nate that if the book isn't found -- and soon -- the world will come to an end. Nate takes the case. He and Sludge cruise up and down and around San Francisco in the limo, tracking down clues. Sticky, icky clues, big and small clues, all-around-the-town clues that take them to a pancake house, over the Golden Gate Bridge, and finally to a place that seems wrong but could be right. Can Nate the Great keep the world from coming to an end? Can he solve his first out-of-town case?