Never Let Go — Gareth Crocker

As he presses a revolver to his head, Reece Cole sees his little daughter's handprints on the windowpane. One last, painful reminder of her all too short life. But then he notices something about the handprints that defies belief. Something that verges on the impossible,

He spends the next few days frantically trying to make sense of what is happening. Then a stranger stops at his gate with a small grey envelope. Inside is a single white card, inscribed with six breathtaking words:
I can bring your daughter back.