Philadelphia homicide detectives Kevin Byrne and Jessica Balzano's first assignment from the Cold Case files is the gruesome murder of a young girl in the Philadelphia Badlands, a bleak and desolate area of crime and depravity. Carefully posed, the lifeless girl is perfectly framed in a square window. Soon another Badlands runaway is found viciously murdered, this time arranged on the roof of a building shaped like a triangle. And as the victims add up, each body tells an increasingly grisly story. A seemingly unrelated crime scene leads Byrne and Balzano to an eccentric older woman who introduces them to a Tangram puzzle, an ancient code of shapes. When the woman takes her own life, she leaves behind a cryptic clue, a word composed of four worn Scrabble tiles: LUDO, the Latin word for game. There is a foul breath of evil blowing through these murderous geometric puzzles and as more runaways vanish and more shapes are revealed, Byrne and Balzano soon realize that the homicidal mastermind plans to complete all seven forms of his dark and twisted Tangram puzzle. Unless they can stop him first.