The amateur sleuths are called to a monastery to restore a herb garden in time for a royal visit - but their pruning and planting is disrupted by the discovery of a corpse. As they investigate the death, the tight-knit community closes in around them.

The duo are invited to help create an Arabian-style garden in Malaga. Before long, a local resident is found dead, and a mysterious landowner is the chief suspect. When it transpires that someone has blocked the mountainside channels on which the new garden will rely for its supply of water, it appears the precious commodity may provide a motive for the killing.