Here comes a relaxed mystery, where the corpse doesn’t show up until two-thirds of the way through the story, when Ellery Queen’s sidekick, Djuna, splashes around on a pool of blood in a totally dark amusement park attraction. Ellery solves the case, amazingly enough, without the assistance of a random beautiful muse.
I especially enjoyed the description of the House of Darkness:
“It was a composite of all haunted houses of fact and fiction.
A diabolic imagination had planned its crazy walls and tumbledown roofs.
It reminded Ellery – although he was tactful enough not to mention it to
Monsieur Duval [the owner] – of a set out of a German motion picture
he had once seen, “The Cabinet of Dr. Caligari.” It wound and leaned
and stuck our fantastically and had broken false windows and doors and
decrepit balconies. Nothing was normal or decent…the real dirty work ,
thought Ellery disconsolately, went on behind those grim surrealistic walls.”
I wish modern amusement park haunted houses could be described so well: my experience is they are designed to not scare or offend anyone. The Cabinet of Dr. Caligari (1920) broke ground with set design, and F.W. Murnau pushed further in Phantom (1922) by having the city fall down upon the hapless main character. But I digress.
The story was another attempt by the cousins to break out of the detective pulp ghetto into the mainstream magazine market. This story appeared in American Magazine (February, 1935). American was a long-lived popular magazine: founded in 1876 as Frank Leslie’s Popular Monthly, it became American Magazine in 1904, and ran until 1956. The cousins were not the only mystery writers to appear in their pages: Arthur Conan Doyle, Agatha Christie, SS Van Dine, Rex Stout, Mary Roberts Rinehart, and Dashiel Hammett, for instance, had all seen their work appear in American Magazine.
The February, 1935 (Volume 119, #3) issue, where The House of Darkness originally appeared, also featured Too Much Water by Don Marquis, “Feud” by Sherwood Anderson, Charlie, by Max Brand, the end of a five part novel by Kathleen Norris, and the beginning of a five part novel by David Garth.
Just six years after losing a literary contest, the cousins had entered the top tier of American popular fiction.
Reading Ellery Queen 
This one also hearkens back to a particular clue used in one of the early novels; I don’t want to spoil it by saying which one. As so often with the Queen cousins, a clue and its meaning can be so stunningly simple that you close the story with an admiring curse and say, “I wish I’d thought of that!”