Ten-year-old Aurora has a mysterious neighbor (Mads Mikkelsen) who kills real-life monsters; he is a hitman for hire. So, when Aurora needs help killing the monster that she believes ate her entire family, she procures his services. Suspecting that Aurora parents may have fallen victim to assassins gunning for him, the neighbor guiltily takes the job. To protect her, he will need to battle an onslaught of assassins and accept that some monsters are real.