Two brothers, Will and Roger, are determined to find out about their father's secret invention which is supposed to end world hunger. As they follow a trial on the floor they start to find much bigger than normal dead animals laying around. They continue walking and they soon find their father's invention, some sort of food which caused the animals to overgrow. They come to the conclusion that the rats got to it first and after them the cats but that something else must have killed them.
They don't find their father so they decide to look for him on the levels upstairs. They take the elevator and as the door opens they find out what killed the other animals, a giant spider which now will devour them too.