In the Great Fire Lucy saves a baby girl from certain death after a woman dropped the bundle out of the window of a burning hotel. The heroic gesture comes after a rather humiliating night of being rejected by a potential lover (Rand, who unknowingly was married, oops).
Lucy raises the child as her own (with the help of her own mother) and names the child Maggie. Several years later (where our story picks up again) Lucy meets again the married man she had hoped to take as a lover. She needs his help as a banker to extend the loan on her bookshop (named the Firebrand after the moniker earned to Miss Woodhull-Claflin for her views on woman's sufragette) and learns that her daughter Maggie is actually Rand's daughter Christine that he thought died in the Great Fire. Since then he was divorced by Maggie/Christine's birth mother and was living all alone with his scars.
Lucy really does not want to tell him about how she became Maggie's mother but does eventually because she knows that it is the right thing to do. Maggie likes her "new" father, but needs her mother too so Rand eventually "proposes" an arrangement. Literally a marriage. Since Lucy had liked him all along it turns into a difficult kind of 'I-want-to-but don't-want-him-to-think-I-do' situation.
It is sort of cute and awkward and not nearly as risque as some of Wiggs' work.