Raven's Gate by Anthony Horowitz

He always knew he was different. First there were the dreams. Then the deaths began. When Matt Freeman gets into trouble with the police, he's sent to be fostered in Yorkshire. It's not long before he senses there's something wrong with his guardian; with the whole village. Then Matt learns about the Old Ones and begins to understand just how he is different. But no one will believe him; no one can help. There is no proof. There is no logic. There is just the Gate.