"I'm not saying the internet made me kill, but it certainly helped." Is there someone online who really grates on you? That friend who's always bragging about their awesome life and endlessly sharing tired memes, and who just doesn't get jokes? Look at your Twitter feed: don't you get cross at the endless rage, the thoughtless bigotry and the pleading for celebrity retweets? Meet Dave, a street fundraiser and fan of cat pictures. He's decided that unfollowing just isn’t enough. He's determined to make the internet a nicer place, whatever it takes. When he killed his best friend's girlfriend, he wasn't planning on changing the world. She was just really annoying on Facebook. But someone saw, and made him an offer. Someone who knows what he's capable of, and wants to use him to take control of the darkness at the heart of the internet. And now the bodies – the comment trolls, the sexual predators, the obnoxious pop stars – are starting to mount up...