This year’s winter in the town of Knottingville is especially harsh. Underground water freezes and expands, creating bumps. Now in early spring, the frost heaves are still enormous and getting bigger. Cracks open up in the ground and release strange odors. Something strange is happening.
Nathaniel investigates and discovers that smells he makes are duplicated by the heaves. He studies the smell sequences and determines them to be a form of communication. Each smell corresponds to a word in the universal language. The frost heaves are wombs for the embryos of an invading alien force!
It is too late to warn anybody. Hatching from their shells of green ice come the Ceiling Walkers with their black, flowing forms. Outside, they hop from tree trunk to tree trunk silently and at high speed, never touching the ground or leaving a trail. Inside, they cling to ceilings with their feet, waiting for the right moment to strike down and drink the blood of the townsfolk with their hundred tiny sucking mouths. Nathaniel, Haticat, Fred, and Doctor Bill must visit every house and open every hiding place to exterminate the bloodsuckers.