All the Old Bargains — Benjamin M. Schutz

Leo Haggerty is hired to find Miranda Benson, a missing teenager. Haggerty finds her with Tony, a pimp who has gotten her into drugs and porno movies. What Haggerty discovers is that Miranda's father had sexually abused her for years and that she left home to get away from her father. Haggerty returns Miranda to her parents with the understanding that her dad will pay for therapy for Miranda and her sister (who was also sexually abused) and that they will be sent to a boarding school and never have to live with their father.