’He looks upon the murders that he did in fact perform as tiresome and regrettable necessities,’ reflected Chief Superintendent Roderick Alleyn on the international crook known as ‘the Jampot’.

But it was Alleyn’s wife Troy who knew ‘the Jampot’ best: she had shared close quarters with him on the tiny pleasure steamer Zodiac on a cruise along the peaceful rivers of ‘Constable country’. And it was she who knew something was badly wrong even before Alleyn was called in to solve the two murders on board…