Set over three explosive days, this is compulsive, heart-pounding storytelling that will keep you on the edge of your seat. He thought she was safe. Then the past came knocking. Seventeen years ago, Inspector Ewert Grens was called to the scene of a brutal crime. A family had been murdered, with only their five-year-old daughter left behind. The girl was placed under witness protection, but while the case went cold, Grens is still haunted by the memory. When he learns that the apartment where the crime took place is now the scene of a mysterious break-in, Grens fears that someone is intent on silencing the only witness. He must race to find her. before they do. 'A perfect example of Scandi noir' The Times 'Roslund has two strong prose styles - dark and darker - and both are on show in KNOCK KNOCK' New York Times.