Sam Haig is identified as a key figure in Merritt Lingard's past. Merritt was last seen with him at a hotel, and according to her abductor, Sam Haig was dead because of her. This connection is a significant lead in the investigation in Episode 4.

Merritt Lingard goes to retrieve William's hat on the ferry but is suddenly grabbed by a man wearing the hat and is abducted. She wakes up inside a sealed, pressurized chamber where she panics and tries to get help, but loud music is played to silence her.

Carl Morck develops the theory that there were two assailants involved in the Leith Park shooting. CCTV footage and physical evidence suggest it would have been impossible for a single shooter to enter quietly or wait inside, indicating multiple attackers.

Carl is dealing with guilt over a past shooting that left his partner paralyzed and a younger officer dead. He also struggles with his responsibilities as a stepfather to Jasper, which complicates his emotional state and therapy sessions with Rachel.

Merritt's return to Mhòr after the attack on William was to attend Harry Jennings's funeral. Harry Jennings was the man who attacked William, making this visit a notable plot point that ties past events to the current investigation.