At the end of Tears for the Giraffe, the previous novel in the series, Precious Ramotswe is engaged to Mr J.L.B. Matekoni, the No 1. Ladies' Detective Agency is firmly established, and all seems to be well. But now, as Morality for Beautiful Girls begins, Mr J.L.B. Matekoni, the hard-working, generous-hearted mechanic and owner of Tlokweng Road Speedy Motors, is behaving strangely. He is uninterested where once he was enthusiastic, full of self-reproach where once he was confident. In short, he is depressed, so much so that he cannot continue to run his business. To make matters worse, the detective agency, despite its success and high reputation, is losing money. Mma Ramotswe's assistant Mma Makutsi is eager for a promotion, and there are now two orphan children whom Mma Ramotswe and Mr J.L.B. Matekoni must raise.

Drastic measures are called for: a merger and major reorganization. The No. 1 Ladies' Detective Agency closes its offices, moves into a small building adjoining the garage, and Mma Makutsi serves as acting manager of Tlokweng Road Speedy Motors, as well as assistant detective, while Mr J.L.B. Matekoni is resting. And in truth the two businesses are not so different. People bring their cars in to have the mystery of their malfunction solved much in the same way people bring in their personal problems to have the detectives diagnose and fix them.

A Government Man, convinced his new sister-in-law is out to kill his younger brother, enlists Mma Ramotswe's services, and while she is working on that case, the director of a beauty pageant asks Mma Makutsi to help him find one "good girl" who will not bring disgrace to the pageant and to Botswana, (no small task, as it turns out). As always with the Precious Ramotswe novels, however, the story of how people live—how they treat each other, how deeply they empathize with others, and how well they respect the customs and morality of Africa—is the real story. And with the ever-engaging Mma Ramotswe at the center of the novel, observing, commenting on, and indeed influencing the world around her, this story comes vibrantly and unforgettably to life.