It's early summer in Stockholm. Agneta and Stellan Broman have just waved off their daughters and grandchildren when the landline phone rings. The caller says just one word: "Geiger." Agneta hangs up, finds her old pistol, kills her husband of fifty years and then disappears from their home without a trace.

Sara Nowak, a police officer in the prostitution unit, is called by a colleague who is investigating the murder. Stellan was a widely loved former television presenter, and Sara grew up next door to the Bromans, spending much of her childhood in their grand house. Both the victim's daughters and Sara are devastated by the killing, and going against all regulations, Sara gets involved in the investigation. It is the beginning of a dark journey, leading back to the Cold War and fatal ideologies, and the truth about Sara's own childhood.