Aisles of Doom

In a town, there's a shop called the Plaza Discount Center, featuring toys of all kinds. It should be a place children love, and it would be save for its shopkeeper, Grendel T.W. Ulcerous. He's evil, but only the children know it, and no one listens to them. We watch what Grendel does to a couple of them. Then, one day, a stranger in a yellow rain slicker comes to town. A confrontation follows. Is it the end of Grendel?