A Whisper of Sorrows (DCI Jack Logan Book 6), J D Kirk

The hunter has become the hunted. Ten years ago, DCI Jack Logan caught the twisted child killer known as Mister Whisper. Two days ago, Mister Whisper escaped. Now, Jack must track down the most ruthless enemy he has ever faced before he can strike again.

But, after ten years behind bars, it isn't just murder that Mister Whisper has in mind. It's revenge.