Knock Knock

He thought she was safe. Then the past came knocking.

Seventeen years ago, Criminal Inspector Ewert Grens was called to the scene of a brutal crime. A family had been murdered, and the only survivor--and witness--was the five-year-old daughter. The girl was placed in the witness protection program, and the case went cold, but years later, Grens is still haunted by the seemingly random slaying, and the little girl who was spared. So when he learns that the apartment where the crime occurred is now the scene of a mysterious break-in, Grens immediately fears that someone is intent on silencing the only witness. He races to find her...before they do.

Meanwhile, someone in the city's criminal underworld is executing weapons smugglers, and has placed former police informant Piet Hoffman's family in grave danger. He must unravel the secret threat to his family, all while keeping secrets of his own. Soon his hunt for answers intertwines with Ewert's, and the two men find themselves in the middle of a criminal conspiracy that is more complicated--and dangerous--than they could have imagined.