The story is set in Néboa, a fictional island off the coast of Galicia. The corpse of a teenager appears during the first night of the entroido carnival in Néboa. The murder mimics the pattern of past killings that occurred in 1919 and 1989, both of which sparked a serial killing row with multiple deaths. Locals believe the killer is the Urco, a wolf headed man from the folk stories. Three Guardia Civil agents, Mónica Ortiz, Carmela Souto and Lieutenant Ferro try to solve the mystery and avoid another serial killing rampage.