Detective Lotte Meerman is convinced the death of Frank Stapel, a painter and decorator, isn't an accident after she and his widow Tessa find a skeleton in a sports bag in his left luggage locker at Amsterdam Central train station.

The remains date from the Second World War and Lotte's colleagues consider it of minor importance . . . until forensic tests show that amongst the bones is the arm bone of a crime boss who recently went missing.