The Shadow is investigating the threat of a Nazi-allied killer from Europe loose on the streets of New York. Meanwhile, Inspector Joe Cardona is investigating a cryptic and threatening message sent to him — "Midnight-Morte-Malmordo" — on a scrap of a cafe's menu. The two intersect as the villainous Malmordo strikes the Cafe De La Morte in Greenwich Village, setting The Shadow on the trail of the rat-faced Malmordo and his gang.
This was intended to be the final Shadow story written by prolific Shadow author Walter B. Gibson, as he had been unceremoniously fired by Street and Smith through the expedient of not renewing Gibson's contract. Gibson himself recounted later that he wrote the novel, all 20,000 or so words, in a single weekend in what he described as a "fugue state" out of frustration over the situation. For the next two years, the identity of "Maxwell Grant" was taken over by Gibson's friend and fellow magician Bruce Eliott. However, Eliott's stories, and the Executive Meddling of the magazine's new editor (who allegedly was not a fan of pulp-style action and wanted to turn the magazine into a "prestige" literary-mystery magazine) caused a sharp drop in sales. Street and Smith responded in 1948 by rehiring Gibson and the previous editor and reformatting the magazine back to its visual and editorial style of the mid-to-late '30s, the classic era of The Shadow. The damage, however was done, and after only a handful of new Gibson-penned stories, the magazine would fold.
"Malmordo" provides examples of:
- Absurdly Spacious Sewer: In line with their "water rat" theme, Malmordo's gang make use of these as shelters/prisons/execution chambers.
- Actually Pretty Funny: The Shadow laughs at Harry's non-clue. Not his usual maniac laugh, but one of genuine humor. Harry finds it at the same time both unsettling and reassuring.
- Badass Bookworm: Commissioner Weston. It appears his being swapped out for Commissioner Barth may have had in part to do with his being reactivated as an Army officer during the war. It's noted that he recently has a much more military bearing around him. As for the "bookworm"? Two entire chapters show him intensely studying Esperanto while doing other tasks.
- Bait-and-Switch: The Gypsy characters are hinted to be in league with Malmordo. Playing on the criminal stereotype of Roma people, this is used brilliantly later in the story when it's established that the Roma have nothing to do and want nothing to do with Malmordo — their only part in the whole affair was that they took pity on him and his band, mistaking them for fellow refugees and so helped them come to America.
- Bat Deduction: The final piece of evidence that Lamont Cranston/The Shadow reveals to prove that Stacy is Malmordo is that he pronounces the letter "Z" like "zee" and not "zed" which an actual Canadian who had spent his working career in Britain would have done
- Booby Trap: Malmordo sets one for The Shadow, by draping his clothes over a chair in a fashion that makes it look like him hunched over, which triggers the entire room to explode when disturbed.
- Foreshadowing: Attentive readers can easily spot the subtle clues that point to the big plot twist — that Stacy is Malmordo.
- From the Latin "Intro Ducere": Weston and others make a leap at an etymology for Malmordo's name, thinking it comes from the Latin mala or "evil" and mortis or "death". It's later revealed that the mal actually means something like "the opposite of" and "Mordo" is a corruption of the word for "rat" or "rodent" in Esperanto, and was Malmordo and his gang's rephrasing of a pejorative name given him.
- Rat Men: Malmordo and his gang are almost always described with rodent characteristics. In fact they're first seen (or heard) jumping off of a docked freighter with a gang of rats. It's later established that the gang chooses granaries, food warehouses and other buildings likely to be rat-infested and deliberately feed the rats to use as guards.
- Roguish Romani: The villain uses prejudice against "Gypsies" to frame them as accomplices in his crimes. The Romani in the story are actually pretty law-abiding sorts.
- Shown Their Work: Gibson put in the effort to add actual Roma and Esperanto phrases into the story to give verisimilitude to the Gypsy characters and the Esperanto-speaking Malmordo.
- Suddenly Always Knew That: The Shadow is fluent in Roma and Esperanto, a trait he uses to get the trust of the Roma.
