S1, E4: While Investigating The Stabbing Death Of His Motherinlaw John Macgibbon Uncovers New Evidence Long Hidden By The Police He Searches For The Final Pieces Of The Puzzle And Is Met With A Letter Left Behind By The Killer Whose Body Had Been Found Drowned Not Far From The Site Of The Crime With This Vital Information Will Macgibbon Be Able To Rest His Search For Reasons For This Tragic Death