How does a banal earthworm become a valuable commodity? Lumbricus terrestris, otherwise known as the Canadian nightcrawler, is the most popular live bait used by recreational anglers throughout the world. Each year, as many as seven hundred million worms are handpicked from Ontario farmland for the bait market, earning the region the undisputed title of worm capital of the world. The Nightcrawlers goes deep into the empirical underground to see how capital confronts a diverse cast of human and nonhuman characters: stubborn worms, wealthy dairy farmers and their precious cow manure, immigrant pickers laboring at night, and worm wholesalers who undercut each other through tax fraud and money laundering. This eccentric tale of worms, cows, and cash reveals the inherent contradictions in capitalism's attempts to commodify the living world—including the soil organisms that are inches beneath our feet.