1) Failure to set up establishing details to make a narrative credible.
At first, not much is revealed about the protagonist, Michael Strang, but as the story develops, he pulls, out of nowhere, exactly the tools and skills that he needs to solve a supernatural mystery.
We are told, early on, that he has been "deeply interested in the anthropological researches of Professor Hendryk Brooler," which says nothing. For all we know, Strang might be an expert on matrilocal kinship in Siberia. Later in the story, after a series of strange events:
"With a bewildered shake of my head, I dismissed the matter from my mind and, picking up a book, settled myself to read. The volume, selected at random, was not one calculated to rid my mind of haunting shadows. It was the extremely rare Dusseldorf edition of Von Junzt’s Nameless Cults, called the Black Book, not because of its iron-clasped leather bindings, but because of its dark contents. Opening the volume at random, I began idly to read the chapter on the summoning of daemons out of the Void. More than ever I sensed a deep and sinister wisdom behind the author’s incredible assertions as I read of the unseen worlds of unholy dimensions which Von Junzt maintains press, horrific and dimly guessed, on our universe, and of the blasphemous inhabitants of those Outer Worlds, which he maintains at times burst terribly through the Veil at the bidding of evil sorcerers, to blast the brains and feast on the blood of men."
Nameless Cults, a book so extremely rare that Strang just happens to find a copy in his living room, just happens to solve the mystery.
Most writers would have prepared for a moment like this with substantiating details, by making Strang a collector of extremely rare books, an historian, a student of the occult, or anything that might justify his having such a book at hand. Here, it shows up from out of the blue.
Also from out of the blue:
"My gaze fell upon a great broadsword hanging on the wall. The weapon had been in the family for eight centuries and had let blood on many a battlefield since it first hung at the girdle of a Crusading ancestor."
Again, this could have been justified, if Strang had been a collector of swords, an expert on the Crusades, a man with a weapons fetish. Instead, what we have is an all-too convenient solution pulled out of a hat.
2) Failures of tone and voice.
Until three quarters of the way through the story, Strang appears to be an ordinary modern man, who speaks in the language of his day with an occasional use of slang ("petting party").
"Good morning, Mr. Stark, sorry to have troubled you. I’m Michael Strang. I live in the last house on the other side of the street. I just dropped in to learn if you’d seen anything of a big Maltese cat recently. [...] It’s my fiance’s cat, though, and she’s broken-hearted over losing it. As you’re her closest neighbor on this side, I thought there was a bare chance that you might have seen the animal."
Later in the story, he suddenly turns into Strang the Barbarian:
"A black fury gripped me, bringing with it the craft that extreme passion often brings. I was going into that dark house, and I was going to hew John Stark’s head from his body with the blade that in old times had severed the necks of Saracens and pirates and traitors....
"'This I do know -- that demoniac lust is no stronger than human hate, and that I will match this blade, which in old days slew witches and warlocks and vampires and werewolves, against the foul legions of Hell itself'....
"'Did not Stark say something about the thing breaking out of its prison?'....
"Now as I stood frozen, and out of that shambles the ghastly fiend came lumbering toward me, my fear was swept away by a red blaze of berserker fury. Swinging up my sword I leaped to meet the horror and the whistling blade sheared off half its tentacles which fell to the floor....
"She lay at my feet in a dead faint, and Bozo [the dog] stood faithfully over her. Aye, I doubt not, if I had lost that grim battle, he would have given up his life to save his mistress when the monster came lurching down the stairs."
3) Poorly visualized action.
Strang, in his berserker fury, attacks the monster:
"With an abhorrent high-pitched squeal, the monster bounded high above my head and stamped terribly downward. The impact of those frightful hoofs shattered my upflung arm like matchwood [...] And with my one good hand I gripped the sword that a saint had blessed in old times against the powers of darkness, and the red wave of battle-lust surged over me.
"The monster wheeled unwieldily toward me, and roaring a wordless warcry I leaped, whirling the great sword through the air with every ounce of my powerful frame behind it."
After more unwieldy wheeling, Strang rescues his fiancée:
"At the foot of the stairs I stumbled over a soft heap [...] With a sob of horror I caught up the girl, crushing her limp form to me....
"I ran from that house as I would flee from Hell, but I halted in the old store-room long enough to sweep a hasty hand over the table where I had found the candles. Several burnt matches littered the table, but I found one unstruck. And I struck it hurriedly and tossed it blazing into a heap of dusty papers near the wall."
He does this while carrying a woman and a sword in his one good hand.
(Eventually, the pain of that arm "shattered like matchwood" will have to reach his brain. That's going to hurt!)
4) A ridiculously long-winded monologue for the sake of exposition.
The most jaw-droppingly bizarre technique in the story appears when Strang finds his fiancée chained up in a monster-haunted house, where silence and a speedy escape are the first priorities. But instead of getting the hell out of there, his fiancée reveals every background detail of the plot, while quoting the villain in full (right down to his multiple adjectives).
"I'll tell you quickly -- then we must run!"
This "telling quickly" requires twelve paragraphs:
"'You do not understand. I see in your eyes that you do not understand. But I will try to make you understand. Men think I am deeply cultured; little do they guess how deep my knowledge is. I have gone further than any man in the arts and sciences. They were toys for paltry brains, I found. I went deeper. I experimented with the occult as some men experiment with science. I found that by certain grim and ancient arts a wise man could tear aside the Veil between the universes and bring unholy shapes into this terrestrial plane. I set to work to prove this thing. You might ask me, why? Why does any scientist make experiments? The proving of the theory is reason enough–the acquiring of knowledge is the end that justifies the means. Your brain would wither and crumble away were I to describe to you the incantations and spells and strange propitiations with which I drew a mewling, squalling, naked thing out of the Void.
"'It was not easy. For months I toiled and studied, delving deep into the ungodly lores of blasphemous books and musty manuscripts. Groping in the blind dark Outer chasms into which I had projected my bodiless will, I first felt the existence and presence of unhallowed beings, and I worked to establish contact with them–to draw one, at least, into this material universe. For long I could only feel it touching the dark borderlands of my own consciousness. Then with grim sacrifices and ancient rituals, I drew it across the gulfs. First it was but a vast anthropomorphic shadow cast upon a wall. I saw its progression from nothingness into the mold and being of this material sphere. I saw when its eyes burned in the shadow, and when the atoms of its nonterrestrial substance swirled and changed and clarified and shrank, and in shrinking, crystallized and became matter as we know it.
"'And there on the floor before me lay the mewling, squalling, naked thing from out the Abyss, and when I saw its nature, even I blenched and my resolution almost failed me.'"
On and on and on, while the monster stomps overhead. She must have taken notes in shorthand.
5) Why harp on this? Why?!?
The only reason to examine a work this poorly crafted is to see how technique can fall apart, and to train ourselves to recognize similar failures of craft that might infest our own work. Lapses in technique do not always glare like neon, as they do here; they can be subtle and concealed. We can find them and resolve them, if we learn to recognize the old stench that bubbles up from hasty writing and lack of attention.