It is South London, UK, in the middle of the 1970s. The summer is long and hot and in Thornton Heath - a quite little suburb - little of note happens. When Charlie Daniels is found dead on his gardening allotment, it appears to be natural causes, but local doctor Lance Elliot isn't so sure. He has questions, such as just how did his patient Wilhelmina Wylie know about the death so quickly when she is housebound and her house is far from the site of the death? And then he discovers that the Thornton Heath Horticultural Society is not as tranquil is at it at first appears, for there are secrets and hidden jealousies. The scathing Inspector Masson doesn't welcome Lance's intervention, but the deaths keep happening around him, and he is inevitably drawn in. He little realises, though, that he is placing those close to him in danger.