Twelve-year-old twins Paul and Judy Hilliard frequently see a candle glowing in a rundown old house down the street from where they live. Adults tell them that they are imagining things. Their search for answers leads them on investigative tour lasting several years. In it they learn of wealth rumored to be stolen from the royal family of Bavaria. Furthermore, the theft is supposedly connected to a former mayor of their city and to a kind, elderly woman who lives across the street. The twins help their elderly neighbor and her disabled granddaughter lead them on many adventures that eventually take them to Bavaria and a royal wedding.