Only recently described by science, the mysterious mushrooms are found in different parts of the world, but they give people the same exact visions. Every year, doctors at a hospital in the Yunnan Province of China brace themselves for an influx of people with an unusual complaint. The patients come with a strikingly odd symptom: visions of pint-sized, elf-like figures – marching under doors, crawling up walls and clinging to furniture. The hospital treats hundreds of these cases every year. All share a common culprit: Lanmaoa asiatica, a type of mushroom that forms symbiotic relationships with pine trees in nearby...