In this ninth volume in the popular series set in Botswana, Mma Ramotswe is drawn deeply into a pair of surprising mysteries. The first starts after she receives the first of a series of threatening letters that say less than kind things about the detective and her firm. It will send her and her assistant, Mma Makutsi on an interesting journey that will highlight that things are not necessarily what they seem.

The second case centers around a young woman who had been adopted from the local orphanage. There seems to be a strong question about her parentage and who may or may not be a part of her family. While the case doesn't have the happy ending that Mma Ramotswe or her client would have wanted, but it does bring about a surprising familial connection for the client.

Mma Makutsi and her fiance are working on getting things ready for their new life, which will start once they are married. As part of the process, they go shopping for a special new bed. He takes her shopping, since his furniture store does not sell beds, and they find a beautiful (and very expensive) bed. He arranges for the bed to be delivered to her home so she can enjoy the new bed before they are united. Unfortunately, she makes an error in scheduling, and the bed is left outside at the start of the rainy season, damaging the bed. Mma Makutsi is left with the trouble of how to tell her future husband of her error ... or to hide it from him.

The Speedy Motors in the title is owned by Mma Ramotswe's husband, Mr. J.L.B. Matekoni. He is looking for his own miracle for their foster daughter, Motholeli, who is confined to a wheelchair after an early childhood illness. They connect with a doctor who specializes in treating children who are confronted with the illness and its side effects. It provides a great deal of hope for a miracle.

Through the cases and Mr. J.L.B. Matekoni's mission, it soon becomes clear that sometimes miracles are not only grand and inspiring/ They can also be found in the world around us: in the little happinesses we find in our friends and family, in our small success, and in the beauty of the world, particularly the beautiful nation of Botswana. It can also be seen in the fact that Mma Makutsi is able to give Charlie, one of Mr. J.L.B. Matekoni's lazy assistants, a compliment for helping to save the day with one of their cases.

The book also has the usual level of humor, which is best exemplified when Grace Makutsi comes face to face with her nemesis, a woman she had gone to school with who has had a great success in her career due to her looks rather than her good grades.

The humor is by no means limited to that, and like the other books in the series, the story's real strength is in the rich characters and comfortable writing style.