The Beast ( Ewert Grens #1 )

Two children are found dead in a basement. Four years later, their murderer escapes from prison. The police know if he is not found quickly, he will kill again. But when their worst fears come true and another child is murdered, the situation spirals out of control. In an atmosphere of hysteria whipped up by the media, 

Fredrik Steffansson, father of the murdered child, decides he must take revenge. His actions will have devastating consequences. Winner of Scandinavia's most prestigious crime-writing award: The Glass Key for Best Crime Novel of the Year.