Newly engaged Mma Ramotswe is not impressed with Mr. J.L.B. Matekoni's maid, Florence Pena. Unknown to him, she has been sleeping in his bed with her men friends. Obvious to Mma Ramotswe is that she does not keep the house clean. The maid, sensing that the forthcoming marriage will involve unpleasant changes in her own life, attempts to plant a gun at Mma Ramotswe's home to have her jailed.
Mr. J.L.B. Matekoni is maneuvered by Mma Potokwane, the matron of the orphan farm, into offering a home to Motholeli and Puso, a sister and brother orphaned in the bush. He worries that this may affect his engagement to Mma Ramotswe. He likes the girl, who displays an aptitude for, and interest in, the work of the garage.
The first case is that of an American woman in her fifties who lost her son Michael Curtin in Africa ten years earlier. Mrs. Curtin suspects he died but does not know and wants resolution. Mma Ramotswe meets the people who were involved in the community to which he belonged while his family lived in Gaborone. His attachment to the community kept him from returning to the US for his time at college. Mma Ramotswe speaks to the secretary in the college where one man from that time now teaches. It is the secretary's last day, and she dislikes the professor for what he did to a relative of hers, and to many other women. Mma Ramotswe encounters the professor, who is a womanizer, known for dishonest manipulation to gain favors from his female students. She mixes lies with the truth to him, in short uses blackmail, to pull the truth of the events from him. She was powerful against him, to keep herself in charge of the situation. The professor had just started seeing the young man's girlfriend Carla, and she was pregnant with the young man's son. Michael encountered the two together in a small hut. The two men fought; Michael ran and fell into a deep ditch (a donga) and broke his neck. Mma Ramotswe feels the goal is to let Mma Curtin come to peace, so she agrees not to bring any of this information to the police, as it ought to have been originally. They buried the son without telling anyone what happened. Next she meets Carla in Zimbabwe where she lives with that child, a son. She agrees to meet the mother of her long ago lover to tell her the story and let her meet her grandson.
Mma Ramotswe sees Mr. J.L.B. Matekoni with the children on their day out shopping for new clothes. She meets them and understands that he has adopted them. She decides he is a very kind man, and takes the children to her house, where the family will live. Mr. J.L.B. Matekoni learns on a call to his garage that his maid has been arrested. Her plan turns against her, as her friend calls the police on her, and she ends up behind bars, all events occurring without her employer being aware of them, save for the end result.
Mma Ramotswe accepts the case of Mr. Badule, a butcher who suspects his wife of an affair. Mma Makutsi expresses her yearning to do detective work, and Mma Ramotswe promotes her to assistant detective, while also retaining her secretarial role. Mma Makutsi follows the wife and talks with the maids at the home where the wife goes. She discovers that the woman's son– unknown to her husband – is the son of another man, himself married to a wealthy wife, who is paying for the boy's private education. Mma Makutsi finds it difficult to tell a lie, but she understands the importance of not hurting the client with information he does not need to know. Forced toreport to the client herself, she tells him his wife is seeing another man so that his son can get the private school education he needs. Mr. Badule does not learn the son is not his biological son, which would crush him. All the adults continue as they had, and the boy stays in school. The solutionof the butcher's case is the first test of Mma Makutsi's detective and diplomatic skills.
Mma Ramotswe gives a small basket as a gift to Mrs. Curtin, explaining the meaning of its designs as being the tears of a giraffe, meaning that we all have something to give, and the giraffe has its tears to give. Mrs. Curtin's newly found grandson, is keen on geology, identifying rocks to Mma Ramotswe as the two walk outside while his mother tells his grandmother the events of ten years earlier. The boy looks at Mma Ramotswe's engagement ring and identifies it as cubic zirconium, not the diamond Mr. J.L.B. Matekoni and she thought they bought.