Roasamond Vivian, a young girl living with her bitter grandfather, yearns for excitement. When Phillip Tempest pays a visit, Rosamond finds herself charmed by him, though he is nearly twice her age and quite obviously "not a saint." She declares that she would gladly pay a price for happiness, and, thinking that she might change him with her love, marries Tempest a month later. She has no idea just how she'll pay for her decision.
The plot is obviously Faustian, with references throughout to Mephistopheles; early in the novel, Rosamond says, "I often feel as if I'd gladly sell my soul to Satan for a year of freedom."