When a man is found brutally murdered, Arch and Fitz suspect it is the work of “The Abstract Killer”, a serial killer who plagued Saint-Pierre long ago and was believed to be dead.
A hit and run victim causes Fitz to confront his undercover past, and when his ex-partner unexpectedly appears, she joins him and Arch in a race against time to stop a money heist.
When a diver mysteriously drowns, Arch and Fitz are drawn into a world of shipwrecks and plundering, leading them to wonder if the infamous waterway Mouth of Hell has claimed yet another victim.
A world-famous violinist and convicted predator dies while performing at his father's funeral, propelling Fitz and Arch into a search for his killer among mourners and those protesting his presence.
Our coroner Natasha is at the heart of the inquiry into her brother's recent murder. Arch and Fitz question how the man, who was reported dead over a year ago, re-appeared.