It’s 1920 and an exciting landmark moment has been reached in Japan: the opening of a new train line near its thriving capital, Tokyo. A locomotive works its way high into the mountains and into a densely forested area, beset by trees and shadows. But one day the train on this new route is stopped in its tracks by the strangest of obstacles: a swarm of ghostly white creepy-crawlies swamping the rails. The arthropods would disappear not long after, but not forever, returning every eight years or so in an enduring mystery that has only recently been solved.