All is not well with the members of the Midsomer Malham Orchid Society. DCI Barnaby and DS Scott find themselves investigating the murder of Madeline Villiers, a member of the Society and as it turns, someone who was selling very rare orchids for huge sums. The autopsy reveals she was poisoned with hemlock. They soon after find Henry Plummer, also a member of the Orchid Society, hanging from the rafters in his garage and his entire orchid collection destroyed. What they learn is that for many members of the Society, collecting orchids are as addictive as drugs and there is no shortage of possible suspects as a result.