In the mountains of madness is the first-person memory of a miskatonic University geologist about a recent expedition led by him to the Antarctic continent and its tragic end. The surviving professor tells how the expedition began, with airplanes and dog sleds, and how on one of the reconnaissance flights they encountered an impressive mountain range, perhaps higher than the Himalayas. A first group reaches its foothills by land and camps at the foot of the mountains. Explorations of the area lead the group to discover a cave inside which they find fourteen fossils of a height superior to the human belonging to beings totally unknown to science: the main body of the organism is barrel-shaped, supported by a series of legs, from its upper end emerges a bouquet of tentacles and has membranous wings retracted on both sides. A second group, with which the narrator travels, loses, after this intriguing information, radio contact with the former, and they head to the place in airplane. The show that awaits you when you arrive is dantesque... Soon after, in an aerial inspection over the mountain range they will make a historical and fascinating discovery...
Many critics have wanted to see in this spooky story a masterful continuation to the mysterious end of E.A. Poe's The Adventures of Arthur Gordon Pym, forerunner and master of Lovecraft.