- By John Dickson Carr
- First published: US: Harper, 1933; UK: Hamish Hamilton, 1933
“It began, like most of Dr. Fell’s adventures, in a bar. It dealt with the reason why a man was found dead on the steps of Traitors’ Gate, at the Tower of London, and with the odd headgear of this man in the golf suit. That was the worst part of it. The whole case threatened for a time to become a nightmare of hats.”
The second Dr. Fell story is one of the best of the lot, in subject-matter, in conception, and in characterisation. The plot ingredients (stolen hats, crossbow bolts, and Poe manuscripts) are bizarre, but Carr’s masterly plotting — as good an example of the ‘onion’ technique as any—turn these ingredients into the perfect blend of seriousness and farce. Paradoxically, the book is both more serious, but lighter in tone than, Hag’s Nook. There is splendid farce in two of Fell’s interviews, which Carr would develop in The Blind Barber. In direct opposition to the farce is the human side: most noticeably, the genuine and human tragedy of Lester Bitton. The revelations concerning the theft of the Poe manuscript, and the identity of the Mad Hatter, are surprising. The murderer is a well-characterised, sympathetic character; and the clues are well-hidden but fair.
2017 addendum: A good, solid detective story, with lots of detail and detection. It may, though, lack the hyperingenuity of Carr at his best.
Blurb (US)

When the Mad Hatter twitched off the headgear of important citizens and disappeared, most people thought it a joke. But the dead body of Philip Driscoll could not be dismissed with a laugh. They found him on the steps of the Traitor’s Gate at the Tower of London, a crossbow bolt through his heart, and on his head a stolen top-hat. The Mad Hatter had left his signature. There were several puzzles for Dr. Fell and Chief Inspector Hadley to unravel. They had to explain the little plaster dolls, the voice, the theft of a manuscript worth ten thousand pounds, and the reason why two hats were stolen from Sir William Bitton in two days. Out of puzzles like these, Mr. Carr weaves the most ingenious and elusive detective story he has written – a problem in deduction that is guaranteed to fascinate and startle you all along the line.
Blurb (UK)

Is Mr. Carr Edgar Wallace’s successor? We believe that he is – and that the Mad Hatter Mystery will make many others share our conviction.
In an old house in Philadelphia, Sir William Bitton discovered the manuscript of a lost story by Edgar Allan Poe, and took it back to England in secret. It seemed to have no connection with the lunatic who was going about London stealing hats. But the manuscript was stolen, and so they called in Dr. Fell. That corpulent and genial old scholar never expected to become involved in a murder case. Yet Bitton’s nephew was found, stabbed through the heart with a crossbow-bolt, on the steps of Traitors’ Gate at the Tower of London – and on the dead man’s head the murderer had placed a stolen top hat.
Against the background of the Tower, Mr. Carr sets forth a problem in deduction which is designed only for the clever reader. Who killed Philip Driscoll? That is the challenge in the most baffling story this author has ever written. The reader may also like to try his wits on such puzzles as the missing hats, the tool-basket, the voice under the tower, and the woman with the queer cuff; but the identity of Driscoll’s murderer is another thing.
Contemporary reviews
Times Literary Supplement (28th September 1933): A neat little plan of part of the Tower of London raises the reader’s expectations at the beginning of this story; for a complicated locality exactly depicted is often the foundation of a precise but ingenious plot. These expectations are soon dashed by exaggeration and improbability, and there is nothing to compensate for this defect. The persons have no reality or character and their behaviour, especially at the end, is quite incredible. The conversation is stilted and featureless; and the author attempts to force the note of horror. It is a pity that more cannot be said for the book, for there are possibilities about Dr. Fell.
NY Evening Post (Norman Klein, 5th August 1933, 80w): Solution: Don’t think you’ll guess it. Rating: Not too high.
Sat R of Lit (5th August 1933, 40w): Fair… Literary-historical background spices mystery which involves stolen Poe mss., erring wife, jealous husband, scatter-brained lover and ponderous but effective sleuth.