The old house on the Trakeborg estate has been empty for many years since its mysterious owner disappeared without a trace. Twelve-year-old twins Linus and Linnea move here for the summer with their restorer mother, who will renovate this house. On the very first night, the boy hears strange sounds behind the wall, and soon finds a key under the broken floorboards. Who could have hidden it there, and most importantly, what door does it open? “The Key to Hinsides” is the first book in a teenage trilogy created by the famous Swedish writer Karin Alvtegen and her son Albin. Together they wrote a fantastic story, full of secrets and adventures, from which it is impossible to tear yourself away. Karin Alvtegen (b. 1965) is known as the author of detective stories and psychological prose. Her books have won Swedish and international literary awards and have been translated into many languages. The author’s detective stories were published in Russian, as well as the novel “The Butterfly Effect” (Gorodets Publishing House, 2020). For Albin Alvtegen (b. 1993), the book “The Key to Hinsides” became a literary debut.