The Hollow Man (The Three Coffins in the USA) is a 1935 locked room mystery novel by the American writer John Dickson Carr, featuring his recurring investigator Gideon Fell.

A few nights later, a visitor concealing his identity with a false face arrives at Grimaud's house and is shown up to his study by the housekeeper, Mme Dumont.

A newspaper reports that minutes after Grimaud's shooting witnesses saw Fley walking alone down a snow-covered cul-de-sac, and heard a voice shout "The second bullet is for you!"

Fell receives word from Transylvania that the three brothers had been imprisoned for bank robbery, and that after escaping his coffin Grimaud had deliberately left the other two to die.

Grimaud had carefully constructed the illusion that Fley had gone into the study, fired at him, then escaped from the window and returned to his own flat to commit suicide.

In fact, Grimaud had gone to Fley's flat, shot him, posed him as a suicide with the gun in his hand, then put on a cardboard overcoat and mask ready to impersonate his own visitor.

In their Catalogue of Crime (2nd edn 1982), Barzun and Taylor note that this lecture is very good indeed: "twenty pages of sound reasoning and fine imagination in lively words".

[3] In The Story of Classic Crime in 100 Books (2017) Martin Edwards called this chapter, in which Dr Fell admits candidly that he is a character in a novel, "an extraordinarily bold move".