Death and Letters: Henry Gamadge #15

Henry Gamadge is summoned to a secluded estate by way of a crossword puzzle, the only means of communication for a widow being held captive by her relatives. They claim she's lost her mind; she thinks they have shut her away to keep her from spilling on her late husband's suspicious suicide. Can Gamadge sort out the secrets of a clan so scandal-averse they would do anything to avoid it?