When one sees a theft committed, it is instinctive for one to immediately alert the authorities and put a stop to it, but is it always the best thing to do? Lucile is faced with such a dilemma when she realizes a little girl is stealing valuable books from the University Library where Lucile works. Her delay in making the report led her, and her roommate Florence, on a wild search that takes her form Chicago to New York, and back through thieves and fire to set things right. With the help of a few acquaintences, Providence, and her own plucky, resourceful spirit, she solves the mystery of the Secret Mark.
