Minna Fontaine was the daughter of a sinister widow whose late husband had made a lifelong study of poisons. Fritz Keller, son of one of the partners in the firm Wagner, Keller and Engleman, has fallen in love with Minna. Keller's father disapproves of Minna's mother and refuses to allow Fritz and Minna to marry. Fritz's friend David Glenney goes to Frankfort and meets Minna and her mother. Will Fritz and the innocent Minna be able to marry, or will she be kept from happiness by the sins of her mother?