Five men are discussing crime in the garden of the Serpentine Club in Washington D.C. when news comes of the death, apparently from an overdose of morphine, of a beautiful and mysterious Argentine woman in a Washington mansion. Four of the men present find themselves engaged in helping the fifth, Commissioner Selden, to investigate the case which becomes stranger and more complex as it progresses.

Clues are plentiful but the trail is a long one, and before Trevor Stoke, a scientist and one of the four, has found its end, the reader has followed with him many a false scent, delighted in many clever deductions, but never guessed the solution. The Capital Murder is a detective story in the true sense of the phrase, but it has all the rapid action, the breath-taking speed of the thriller.

The Capital Murder was first published in 1932. This title includes racial caricatures and epithets that may not be suitable for all readers. This edition includes both introduction and afterword by detective fiction historian Curtis Evans. The introduction looks at the question of who exactly wrote The Capital Murder under the pseudonym, James Z. Alner. The afterword discusses race and bigotry in the context of these early mysteries and detective fiction.