Cameron, Ann. Julian, Secret Agent, Random House, New York, N.Y., 1988.
From rescuing a dog stuck in a hot car to keeping a toddler from drowning, Secret agent Julian, Huey, and Gloria have done a nice bit of crime-busting. But what they really want is to nab a real live bank robber and get the big $25,000 reward! And just when it looks like they might get their man, the police chief steps in, and the super sleuths find that they're the ones who are in trouble, with a capital T!
Krulik, Nancy E.. The Adventures of Mary Kate & Ashley: The Case of the Fun House Mystery, Scholastic, Inc., 1996.
The twins find mysteries to solve Wherever they go. Even at the Tons of Fun Amusement Park. It was really fun at the park, until they entered the Fun House. Something big and fuzzy grabs Mary Kate's arm and that's when the mystery begins.
Warner, Gertrude Chandler. The Boxcar Children: The Mystery of the Missing Cat, Scholastic, Inc., New York, N.Y., 1994.
Mr. Spotzie's cat is missing. The Boxcar children set out to find it using Lost Cat posters and door-to-door searching with the cat's photograph. Along the way they encounter some strange characters, receive frightening phone calls, and even find a cat that looks just like Spotzie-but is it? The more they search, the more mysterious the mystery becomes.