Kevin Delavan wants only one thing for his fifteenth birthday: a Polaroid Sun 660. There's something wrong with his gift, though. No matter where Kevin Delevan aims the camera, it produces a photograph of an enormous, vicious dog. In each successive picture, the menacing creature draws nearer to the flat surface of the Polaroid film as if it intends to break through. When old Pop Merill, the town's sharpest trader, gets wind of this phenomenon, he envisions a way to profit from it. But the Sun Dog, a beast that shouldn't exist at all, turns out to be a very dangerous investment.