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...