A book about the true role and place of parasites in nature, about the parasite as the driving force of evolution. About their influence on the immune system and on the sexual behavior of animals, and possibly on the need for gender division in general. About the symbiosis between the parasite and the host. About the work and discoveries of scientists, about how to learn to live in a world of parasites, why you don’t always have to fight them, and how a parasite can save our planet.