Mrs. Pollifax Pursued

By Dorothy Gilman

Mrs. Pollifax discovers Kadi Hopkirk, a young girl who has been hiding in her hall closet. After hearing a weird story of Kadi running from kidnappers, and seeing a suspicious white van driving up & down the street for hours, Mrs. Pollifax jumps to the rescue. A phone call helicopter ride later, Mrs. Pollifax and Kadi go undercover at a circus until they can figure what's going on.

I like series that you can jump in the middle of and not be completely confused.  Good thing this storyline is good, because I had no idea this was number eleven.