The Mad Hatters of Washington Square were not only mad but vicious -- "nasty people" as their neighbors were prone to whisper. So when the worst of the lot, old Emily Hatter, was found murdered, no one was particularly upset, except possibly Louisa Campion, her deaf, dumb, and blind daughter by a former marriage. In this tangled web, not one of the family was above suspicion. There were Barbara, the Delphic oracle of New York's intelligentsia, whose abnormality bordered on genius; Conrad, who loved liquor but couldn't hold it; Jackie, his son, with a wily brain and an inspired gift for inventing cruelties; and Jill, the eternal debutante, who experimented with Life with a capital L. But when the clues began to point to Emily's husband, York, proved dead beyond a doubt, Inspector Thumm turned in desperation to his old friend Drury Lane, the famous actor, whose brilliant analysis and solution of the case proved "The Tragedy of Y" a tragedy indeed.

Seems to be a case of murder by a dead man. EQ's first mathematics-based solution, in The Tragedy of Y, seems modeled on the similar math-based deductions in Chapter 9 of S.S. Van Dine's 'The Benson Murder Case' (1926). The use of mathematics seems related to EQ's deep commitment to logic and reasoning. Some critics have described some aspects of the plot as silly: the murderer bludgeons his victim to death with a mandolin because the instructions called for 'a blunt instrument'. There is a difference between silliness and improbability.