First published in 1933, ''He Dies and Makes no Sign'' by Molly Thynne (d. 1950), public domain worldwide. The final mystery by Thynne also features Constantine and Detective Inspector Arkwright. In  He Dies and Makes No Sign  (1933) Constantine is summoned by the Duchess of Steynes to help her talk sense into her son who is proposing to marry Betty Anthony, the granddaughter of an obscure violinist, Julius Anthony. When Constantine meets the girl he finds her charming and worthy of marrying the heir to a duchy and is determined to support the match. However Betty is deeply troubled because her grandfather has disappeared. Constantine calls on the aid of Arkwright to find Anthony and when the old man’s body is discovered in suspicious circumstances, their investigations lead them to uncover a dark conspiracy.--The Golden Age, Molly Thynne (1881-1950) by Carol Westron