Dublin, between the wars: Captain Hastings has come to Ireland to meet the family of Anne Foster, the woman he admires — and quickly decides that being introduced to a houseful of O'Riordans is more perilous than any battlefield. Over one civilised pint at a public house called The Stag's Head, a family quarrel turns into a genuine puzzle when Uncle Seamus produces a codicil to old Patrick Aloysius's will: a late addition that would rewrite an inheritance, signed by witnesses who may or may not have existed. With Anne's relations circling, a forger's clever work to expose, and a small glove-stealing spaniel named Pip underfoot, Hastings must prove that a name copied from a directory is not the same as a signature. The Stag's Head Has Lost His Crown is an original Golden Age-style mystery — a witty comedy of family, forgery, and the small mistakes that betray a liar.