A short story by H.P. Lovecraft, first published in Weird Tales in August 1931. Although it makes numerous references to the Cthulhu Mythos, the story is not a central part of the mythos, but reflects a shift in Lovecraft's writing at this time towards Science Fiction. The story introduces the Mi-Go, an extraterrestrial race of fungoid creatures.In 2011 a film version was produced by Sean Branney, Andrew Leman, and David Robertson and distributed by the HP Lovecraft Historical Society. As per HPLS's The Call of Cthulhu, it uses the Mythoscope blend of vintage and modern filming techniques to produce the look of a 1930s-era Universal Horror film, through given the era this one is a talkie instead of a silent film.
The film and short story have the following tropes:
Ascended Extra: The characters of Wilmarth's three friends at Miskatonic University were developed from Call of Cthulhu role-playing characters created by the filmmakers years before.
George Akeley didn't make any physical appearances in the original story.
Action Survivor: Wilmarth is a sheltered academic, but according to other stories set in the Cthulhu Mythos survives to old age. In the film though he's captured by the Mi-Go and his fate is uncertain.
Adaptation Expansion: The movie depicts the events of the short story but adds a 'third act'. Where the book ends with the protagonists' flight from Akeley's farm and back home, the movie goes on to have him thwart a ritual preceding an Alien Invasion by the Mi-Go, and fight them in a mid-air combat scene. Since the ending is no less Lovecraftian for it, general consensus is that the movie is, as per HPLS's silent movie The Call of Cthulhu, a loyal adaptation of the Cthulhu Mythos to film.
Alien Invasion: In the film. In the short story the Mi-Go are only here for mining and research purposes, and don't harm humans as long as they stay away, as conquering Earth would be too much trouble.
Black Speech: Nathaniel Ward quickly switches off the phonograph when Wilmarth says he's been listening to the wax cylinder recording of the cultist ceremony throughout the night.
Blue and Orange Morality: The Mi-Go have long been Ur Examples for this trope: most people would see the extraction of a brain and putting it in a canister as a morally-questionable act; for them it's a reward.
In the film they do this to Wilmarth, after he ruins their ritual and destroys their stone circle, despite having said that he's unworthy, uninteresting and weak-willed earlier that night.
Brain in a Jar: The Trope Codifier — the alien Mi-Go place living human brains in cylinders to transport them through space to other planets. Unlike later versions of the trope, the cylinders are not transparent (though they are in the film).
California Doubling: Averted with location filming in Vermont and Massachusetts (with Mount Holyoke College as Miskatonic University).
Cat Scare: Hannah grabs Wilmarth's shoulder while he's listening in on the cultists.
Epistolary Novel: The short story consists almost entirely of a correspondence of letters exchanged between the first-person narrator and another character, until the protagonist decides to visit his penfriend in person.
Evil-Detecting Cat: In a Missing Trailer Scene Wilmarth listens to a wax cylinder recording of a man spouting occult ravings while a cat sits impassively nearby. Suddenly ANOTHER voice cuts in on the recording, and the cat startles and hisses.
Eye Lights Out: The binocular device B-67 uses to see winks out when he's killed.
Hero of Another Story: Nathaniel Ward, one of Wilmarth's colleagues at the Miskatonic University, and the one who tries hardest to convince him not to investigate the Mi-Go, seems to be a recurring character in HPLHS stories. In the movie, it is mentioned that he has encountered various cults before, and he uses the scarring of his left hand to try warn Wilmarth that "he doesn't want to know the truth". In addition to this, he co-authored with Wilmarth a monograph available for purchase at the HPLHS Bazaar. Last but not least, the Dark Adventure Radio Theatrewebsite makes mention of our hearing "some Nate Ward stories" in audio-drama form one day.
Heroic Sacrifice: Subverted. After the Mi-Go kill Hannah, Wilmarth decides to crash his biplane into the sacred circle used to create wormholes. As the plane dives we Smash to Black, yet his voiceover continues as if he's still alive until we discover he's in a brain cylinder.
Hologram: Akeley gets Wilmarth to hook up one of the brain cylinders to a machine. Wilmarth is in the midst of saying that he's not going to be fooled by some parlour trick with a radio, when he's shocked to see B-67's head projected via hologram, speaking back to him.
Hope Spot: Hannah hitting the Mi-Go clamped to their wing in the face. Then another Mi-Go swoops down and plucks her out of the cockpit, dropping her from a great height.
Idiot Ball: (short story) Wilmarth walks straight into the most obvious trap ever devised, even giving a lengthy monologue over how it can't possibly be a dangerous situation. Fortunately the aliens are just as stupid, and do nothing besides drug his coffee which he doesn't drink, giving him a chance to realize what an idiot he was and run away.
Science Marches On: The Mi-Go use their wings to fly through the 'aether' of space; they can also use them (less effectively) in Earth's atmosphere. The film instead has the Mi-Go using mechanical wings strapped to their backs, and the advance party making the journey via spacecraft so they can open a 'spirit door' to their planet so the invasion force can come through.