In The Sun Dog the source of terror is a simple Polaroid camera owned by a 15-year-old boy in the small town of Castle Rock, Maine. No matter where Kevin Delevan aims the camera, it produces a photograph of an enormous, ugly, vicious looking 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 Merrill, 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.