Forty years ago, the glamorous Maria Turquand was brutally murdered in her hotel room and the killer was ever found...
But Edinburgh's dark heart is up for grabs but has criminal mastermind and Rebus's long-time adversary, Big Ger Cafferty, really settled down for retirement?
Or is he hiding in the shadows until Edinburgh is once more ripe for the picking?
Old enemies. New crimes. Rebus may be off the force, but he certainly isn't off the case.