I read a lot of mystery novels. Some are crime stories (Donald Westlake’s very funny Dortmunder books, for instance), but most are whodunits. In a whodunit, the author has to keep you guessing about who committed the murder, and possibly how and why, until the very end.
In real life, most murders are sordid affairs. In a bar fight or a marriage gone bad, there’s seldom any doubt about who did the killing. The authors of whodunits, on the other hand, have to go to great lengths to devise crimes that are mystifying.
As a result, the reader is quite often asked to swallow some strange ideas about human behavior.
John Dickson Carr, who also wrote as Carter Dickson, was the master of the locked-room mystery. A corpse is found in a room that is locked on the inside, and the reader is assured that there are no false panels or secret passages. How could such a thing possibly happen? The truth, when revealed, is both astonishing and logical — but with one proviso. You’re asked to accept that the murderer would really have done all that tap-dancing and tightrope-walking in order to rid the world of the victim.
In The Judas Window, a man is found, in a locked room, with an arrow driven through his chest. He’s not, in this particular book, alone, and his companion (who has been drugged and is unconscious while the crime is being committed) is soon arrested and tried for murder, because nobody else could possibly have done it.
If you want to read The Judas Window, you should stop here. Spoilers follow.
The solution to the puzzle, when Sir Henry Merrivale (in one of his less slapstick appearances) eventually reveals it, relies on the construction of 19th century home fittings, as the book was written in the 1930s. The murderer has prepared for her crime by unscrewing the outer doorknob in the door (hours or days earlier) and tying a long piece of string to the inner doorknob. After the victim has locked the door, the murderer removes the outer doorknob and lowers the inner one down on the string. The victim, seeing the doorknob mysteriously dangling, naturally comes over to the door to investigate and leans forward to look through the hole in the latch mechanism.
At this point the murderer fires the arrow through the hole using a crossbow, driving the arrow into the victim’s chest. She then hauls the inner doorknob back up on its string, removes the string, reattaches the outer doorknob, hides the crossbow — and presto, a locked room mystery.
As we savor the faultless logic of the solution, however, we’re asked to ignore the killer’s blind trust in her own luck. First, the intended victim might not even notice the doorknob dangling from the string. That would leave her in a quandary. Second, the hole left when the doorknob shaft is removed is not more than a centimeter across. It’s bound to be very difficult to aim the crossbow through the hole while also looking through the hole — so how is she to judge when the moment has arrived to fire? Third and most egregious, what if she misses? What if she only manages to shoot her intended victim in the arm, or in a grazing wound across his rib cage? If that happens, her guilt will be obvious to everyone.
No, if this woman were really intent on murder, she would choose a more reliable method. The plot of the mystery hangs dangling like a detached doorknob on the thread of her perversity.