JOHN DICKSON CARR. “The Third Bullet.” Colonel Marquis #1. Novella. First published as a novel in 1937 under Carr’s “Carter Dickson” pen name (Hodder & Stoughton, UK). A shorter version appeared in Ellery Queen’s Mystery Magazine, January 1948 (cut by perhaps 20%). Collected in The Third Bullet and Other Stories (Hamish Hamilton, UK, hardcover, 1954; Harper & Bros., US, hardcover, 1954). Collected in Locked Room Puzzles, edited by Martin H. Greenberg & Bill Pronzini (Academy Chicago, paperback, 1986).

   This one is a good one, but only if you’re already a fan of locked room mysteries. If you’re not, I don’t think it will go down well enough to convert you. It’s too single-minded as to the plot, with the barest amount of time spent of either the setting or the characters. But for the record, here’s the basic setup and hold on tight. It’s complicated:

   A murder is committed while the police are watching from the outside through a window and while another policeman is knocking on the only inside door leading to a hall inside the house. The windows are sealed tight (but footsteps are found leading from one of the windows). Only one person was in the room, other than the victim. No one else went in nor went out. No one was hiding inside.

   Two guns are found in the room. One was the one the suspect used; the other is found hidden in a vase. However — and this is a big “however” — ballistics show that neither one was used to kill the victim, a judge who had previously sentenced the suspect quite severely (flogging as well as a prison term).

   The investigation begins on page one, and it continues non-stop until the case is solved. Colonel Marquis is clearly a forerunner of Colonel March, one of Carr’s other more well-known detectives. Even if this was his only appearance, which is likely, he’s the sort of fellow who relishes a case such as this one, and almost as much as I do. The basic explanation is both very intricate and very simple, but the latter doesn’t mean I solved it before Colonel Marquis does.

   To my mind, very nicely done.