The Katharina code

Katharina went missing twenty-four years ago. Each year on the anniversary of her disappearance Chief Inspector William Wisting visits her husband, the man he could never help. He re-reads her files, searching for the answer he could never find. The code he could never solve. Until now. This year is going to be different. Another woman is missing. And so is Katharina's husband. Wisting has to find him, but is he rescuing a dear friend, or playing a deadly game?