Payback — Graham Marks

You know when you do something that you instantly regret? Like picking up something that doesn't belong to you, just to have a quick look at it? Well that's how it starts for Greg. In the park, he sees it lying there; a smooth, black oblong of glass. But as soon as he touches it, his life is altered. Now there's a voice in his head, and everywhere Greg looks someone is ready to die...