If you are worried about spoilers you can stop reading now.
Smith decided to temporarily do away with Mr. J.L.B. Matekoni in this episode, for reasons that are not entirely clear. It may be that he needed to make room to show the hidden talents of Grace Makutsi, who proves to be an inspired manager and a quite capable mechanic. Or maybe the author needed some way of making Mr. J.L.B. Matekoni a little unpredictable: it is probably hard to make a really decent character interesting. Anyway, it was a bit worrisome; but we can feel confident in these novels that nothing too horrible is likely to befall any of the main characters.
The principal story line is a series of apparent poisonings at the house of the brother of a government official. Mma Ramotswe basically goes undercover in the household and, as we have come to expect, solves the mystery with her usual technique of talking to people and really listening to what they say. It’s all quite satisfying and, in a roundabout way, instructive.