The parents and grandparents of the brothers Teo and Tuukka are the owners of an obscure hotel in the book Hotelli Hämärä ja ullakon arvoitus (Hotel Gloomy and the Mystery of the Attic). In this vivid story the boys and their friend Leila decide to examine why they can see odd light and a shadow of a child in the window of the attic and hear strange voices upstairs. The children solve the mystery with the help of guinea pigs, an old guest book and a toy museum.
The book is illustrated by Silja-Maria Wihersaari who is both an illustrator and textile print designer. Mila Teräs has written many books both for adults and children. Sininen huone (Blue room) was on the IBBY Honour List in 2007.