The body of a man is found hanging in an empty house. To the Edinburgh police force, this appears to be a simple suicide case. But something about the scene strikes Detective Inspector Tony McLean as off. Days later another body is found hanging from an identical rope, with a noose tied in the identical way. McLean is convinced that these people are either being murdered or somehow coerced into suicide. Then a third body is found.

Under pressure from his superiors to wrap the case up quickly and neatly, McLean must also deal with the fallout of his last big investigation and complications in his personal life. But the deeper he digs, the more he comes to believe that something dark and sinister is stalking Edinburgh's streets. Will he be able to stop it before someone else succumbs to the hangman's song?