When Tommy and Tuppence Beresford moved to a quiet English village, they were looking forward to a peaceful retirement. But, as they soon discovered, their rambling old house held both secrets and dangers. Who was Mary Jordan? Why had someone left a code message in an old book saying that she "did not die naturally"? And what was the significance of 'Oxford' and 'Cambridge'? Once more, ingenuity and insight are called for as the pair, along with Hannibal the dog, are drawn into old mysteries and new dangers.