For centuries, humanity has waged war against parasitic worms, yet nature rarely draws clean lines between enemy and ally. A new study invites a quiet reconsideration: proteins secreted by Fasciola hepatica, a flatworm long regarded as a liver pest, appear to calm the very immune storms that drive rheumatoid arthritis in rat models. The finding belongs to a growing body of thought suggesting that organisms we have spent generations eradicating may carry, within their chemistry, lessons about immune balance we have not yet learned to read.