The murder of a female GP in a rural playground in front of numerous witnesses draws a group of detectives into an ever-darkening mystery that takes them across Europe, aided by mysterious notes sent by the "Ghost Detective".

From the cop with a bullet in his brain, whose amnesia leaves him doubtful of his own moral compass; to the drug-lord driven by a profound personal tragedy, risking it all on one last deal; to the brilliantly lethal puppet-master who gradually emerges from the shadows to bring the story to its shocking climax – The Shadow Line explores the morality of these characters as they negotiate the repercussions of Wratten's death and attempt to navigate the fine line between right and wrong...