Everything you need to understand or teach After All These Years by Susan Isaacs.
The novel's concern with marital and economic vulnerability, and its distrust of authority figures, do not carry a negative charge, because justice is ultimately done. Rosie's own wit and daring, and the aid of a few good friends, help her discover the real murderer.
Along the way, on the lam, she confronts perils that test her inner self even more than they frighten her. The theme that emerges is one of qualified hope. A brave and resourceful person can overcome outrageous fate, but she has to be willing to take outrageous risks. It is a perennial American belief, still received eagerly by most readers.
A related theme, perhaps a more innovative one, relates to the nature of the risks Rosie is prepared to take. After All These Years shows a traditionally feminine heroine performing morally ambiguous acts. Breaking-and-entering and physical self-defense go with the territory for P.I.s...