Bunch Courtney's hopes for a quiet market-day lunch with her sister are shattered when a Dutch refugee dies a horribly painful death before their eyes. A few days later Bunch receives a letter from her old friend Cecile saying that her father, Professor Benoir, has been murdered in an eerily similar fashion. Two deaths by poisoning in a single week. Co-incidence? Bunch does not believe that any more than Chief Inspector William Wright.

Set against a backdrop of escalating war and the massed internments of 1940, the pair are drawn together in a race to prevent the murderer from striking again.