A mysterious and enormous hound is prowling the dark spaces of Trolberg, leaving a trail of panic in its wake. But Hilda has an entirely different mystery unfolding right inside her own home. She has just stumbled upon Tontu, a mischievous house spirit known as a Nisse, who reveals a hidden network of secret passages running behind the walls of the city. These magical spaces are supposed to be safe havens for the house spirits, but someone or something has been ruthlessly ransacking them. As you dive into this beautifully illustrated graphic novel, you will join Hilda on a desperate quest to help her new outcast friend. The local authorities are too busy hunting the terrifying Black Hound to care about a homeless house spirit, so it is entirely up to Hilda to uncover the truth. You will need your sharpest detective skills as the search for the missing items pulls Hilda deeper into the mysterious world of the Nisse. This thrilling magical mystery perfectly balances eerie suspense with the heartwarming loyalty that makes Hilda an unstoppable explorer.