Botanist Rosemary Boxer visits her friend Daniel Kellaway in connection with a grant for her university, and Daniel asks her to check out why several trees in the grounds of his country house are dying. Daniel is also suffering badly from skin problems.

Meanwhile, Laura Thyme has left her husband, and she goes to see a friend called Sam - shortly before Sam is killed in a mysterious car crash.

Rosemary and Laura meet and strike up a friendship, and they begin to work together on investigating Sam's accident and the dying trees. Then Rosemary gets sacked from her job at the university, and she finds Daniel on the ground having fallen out of his bedroom window. He says he saw his house-keeper prowling around with a knife.

The duo visit Daniel in hospital, where his eczema is getting better, despite not using his medication for it - and they begin to put two and two together.