Masquerade — Phyllis A. Humphrey

Red-haired Ginger Maddox is the only female broker in a San Francisco stock brokerage. When handsome Neil Cameron opens an account, saying that his maiden aunts referred him to her, she finds herself unwittingly mixing business with pleasure. However, Neil is often mysterious and his aunts want her to keep some secrets from their nephew, making Ginger suspect a masquerade. As their romance escalates, so do the strange events, ending with Ginger's suspicion that Neil is involved in illegal insider trading. Worse, he may have courted her purely to investigate what she knew. Is Neil really innocent? Or will Ginger's impulsiveness doom their love?