It's early May in Oslo, but a brutal heat wave has coincided with an alarming increase in violent crime. The latest instance sends police investigator Hanne Wilhelmsen to a macabre crime scene outside of town. An abandoned shed is covered in blood, with an eight-digit number on one wall. There is no body. Is it a prank or foul play? Is it even human blood? As more such cases appear, Hanne's colleague makes a startling discovery: they are the filing numbers of foreign immigrants. All female, all missing.