They are supposed to be at rest. So why are their graves empty? A breath-taking Scandi thriller by a multi-award-winning international bestseller.'If you thrill to the chills of Scandinavian noir, chances are you've read something by Anders Roslund. He has two strong prose styles - dark and darker' New York Times Two little girls go missing on the same day in Stockholm. Their disappearances are never explained. In time, the investigations are abandoned.A chance discovery puts Detective Ewert Grens back on the trail five years later. His own personal trauma makes him determined to find out what happened to these children who were snatched from a supermarket and a car park and never seen again and whose coffins lie empty in the local graveyard. His search leads him into the most repulsive recesses of the dark web and the discovery of a paedophile ring that can only be cracked from the inside. Grens is forced call upon his retired partner, Piet Hoffman, the best undercover operative he knows, to try to infiltrate the group. They will have only one chance - but are they up to the darkest challenge of their lives?'Grens is an eccentric, alienated, socially inept hero worthy of comparison with Swedish mystery master Henning Mankell's Inspector Kurt Wallander' Wall Street JournalPRAISE FOR KNOCK, KNOCK-'A perfect example of Scandi noir' The Times'A complex, white-knuckle read' ObserverShortlisted for the 2021 MAX Zilveren Vleermuis award