""The Targ are a warlike people from a distant galaxy whose own planet, Nedali, is running out of resources. The most valuable one being water."" He looked at the children and realised they didn't quite understand. ""Aliens are going to take over the Earth,"" he said, ""and you have to stop them.""Siblings Timmy, Adam and Salma are surprised by an unexpected visitor and the message he brings that the Earth is in danger. Do they refuse to help, or will they take up the challenge to save the world and become heroes?