The killer is taking his victims in the coldest, most calculating way possible – engineering slow and painful deaths by poison, with his victims entirely unaware of the drugs flooding their bloodstream until it’s too late.

But how do you catch a killer who hides in the shadows? A killer whose pleasure comes from watching pain from afar? Faced with their most difficult case yet, Callanach and Turner soon realise they face a seemingly impossible task…

‘A very sinister premise and an intriguing killer’s voice. Highly recommended.’ James Oswald

‘Relentless pace, devilish cleverness and a laser-sharp focus on plot.’ Chris Brookmyre

‘Without doubt, this is one of the best detective series I have read.’ Woman’s Way Magazine