1801, working for an agency fighting against supernatural Gustave is 24 when he discovers a baby born of a werewolf mother. As he cannot deliver the child to his colleagues who would kill him, he decides to adopt him. Seveteen years later, the discovery of a portrait of his adoptive son in the pocket of a supernatural creature upsets the balance of his life : awaking the suspicions of a co-worker and revealing that someone is looking for his son.