The note read:

"Will the gentleman who took by mistake a copy of Bunyan's Life and Death of Mr. Badman, return it as soon as possible, as the book is in demand."

On holiday in Keldstone visiting his nephew, Jim, blanket manufacturer Athelstan Digby agrees to look after the old bookshop on the ground floor of his lodgings while his hosts are away. On the first day of his tenure, a vicar, a chauffeur and an out-of-town stranger enquire after The Life and Death of Mr. Badman by John Bunyan. When a copy mysteriously arrives at the shop in a bundle of books brought in by a young scamp, and is subsequently stolen, Digby moves to investigate the significance of the book along with his nephew, and the two are soon embroiled in a case in which the stakes have risen from antiquarian book-pinching to ruthless murder.