The suicide of a sales clerk at the box office of a London cinema leaves another girl in fear for her life. Persuaded to seek help from Scotland Yard, Miss Darke confides in Inspector Joseph French about a gambling scam by a mysterious trio of crooks and that she believes her friend was murdered. When the girl fails to turn up the next day, and the police later find her body, French's inquiries reveal that similar girls have also been murdered, all linked by their jobs and by a sinister stranger with a purple scar

Konrad Sejer must face down his memories and fears as he struggles to determine why the corpses of troubled young men keep surfacing in local lakes. As Sejer begins to feel his age weigh on him, he wonders if he has the strength to pursue the elusive explanations for human evil.