Shortly after Olaf Palme's assassination, Stig Engström begins his quest for attention as a crime-scene witness; divisions among police hinder the investigation.

Realizing Engström's story doesn't add up, Irvell starts turning up the heat; decades after the murder, a journalist starts reinvestigating the case.

Irvell's steady methods turn up more evidence to implicate Engström, but Holmér's stubborn tunnel vision leads investigators into a dead end.

Police railroad another suspect; desperate for more attention, Engström continues to speak out; Thomas tries to connect Engström to the gun.

His mental health deteriorating, Engström's life falls to pieces; years later, a prosecutor revisits the case and makes a momentous announcement.