The admitted master of this subgenre was John Dickson Carr, who wrote several mystery novels that might be classified as “locked-room” mysteries.
In 1935's The Hollow Man — also known by its American title, The Three Coffins — we have the epitome of the locked-room mystery. Not only is the book the exemplar of the type, but a whole chapter in the book (“Chapter 17: The Locked Room Lecture”) is devoted to a lecture by Carr’s main detective, Dr. Gideon Fell, on the topic of “locked room” murders. The novel is the sixth Gideon Fell novel out of a total of twenty-three.
Gideon Fell is a British scholar, though his area of study is unclear. When first introduced, he is working on an English dictionary (which suggests a nod to the celebrated Samuel Johnson), but in later books, he seems to be working on a scholarly treatment of the beer-drinking habits of the English — a scholarly endeavor many of us could get behind. (Are you listening, Boulevard?) Like Samuel Johnson, Fell seems to be an expert in just about everything, but unlike Johnson, he is morbidly obese, and uses a cane to get around.
One of the conventions of detective fiction, especially the classic form, is for some person in the story to make some statement about how, “in detective stories,” something would play out in such and such a way, thereby suggesting that the story we are reading is not fiction, but real.
In this novel, when one of Dr. Fell’s friends objects to his about to enter upon a lecture upon the locked room mystery, Fell replies that “we’re in a detective story, and we don’t fool the reader by pretending we’re not. Let’s not invent elaborate excuses to drag in a discussion of detective stories. Let’s candidly glory in the noblest pursuits possible to characters in a book.” So, instead of carrying on the charade that his characters are real, we have his main character candidly admit that he is a fictional character, who glories in it. This kind of self-awareness on the part of a fictional character is something we might expect in a book written in the last 20 years, but not in a popular mystery written during the Golden Age of classic detective fiction. Admittedly, once this admission has been made, it not repeated, and the “illusion” of the world of the book continues as if there had not been this brief confession to the reader.
I’m thinking that Carr, who very much loved the form of the locked room mystery, the form in which the very act of the murder seems to have been impossible, felt it necessary to set forth his thoughts on this form, and lay out its possibilities and rules. And one of the suggestions he makes — he stops short of making this a “rule” — is that the world “improbable” should not be uttered in detective fiction, for it is a commonplace that the least likely suspect is often the guilty party, hid in plain sight all along by a clever author, and that authors of classic mysteries should be upfront about such a convention.
As a puzzle, in which there are two impossible murders: the murder of Professor Grimaud in a locked room by an assailant who mysteriously disappears, leaving no tracks in the snow, and the murder of Pierre Fley, an illusionist, who had threatened Grimaud, who is also the most “likely” culprit, in an empty street where two witnesses saw no one but Fley, who fell dead following shots that seemed to come from nowhere. Complicating matters is that Fley seems to have been killed prior to Grimaud himself. As a puzzle, this is quite an excellent one, in that the “impossible” murders are rather simply explained by Fell in the concluding chapter, and Carr did, indeed, demonstrate that he had played fair.
But Carr fails to produce compelling characters. In many ways, even the main characters might be interchangeable, given letters for names as if the whole book were a problem in calculus of several variables. Unlike Christie, or Marsh, or Sayers, who create some compelling characters in their detective novels, Carr, at least in this outing with Dr. Fell, fails to do so.