At Salem, Massachusetts, cemetery caretaker "Old Masson" must deal with a teeming colony of abnormally large rats that are cutting into his grave-robbing profits; the subterranean rodents drag away newly buried corpses from holes gnawed into the coffins. One night Masson attempts to rob a grave only to see the corpse pulled into a burrow by a rat. In an attempt to retrieve the valuables Masson crawls into the tunnels after the body. After a short time he realizes how dangerous his situation is and tries to turn back, being set upon by the rats which he fends off. As he climbs back up the tunnel Masson eventually comes face-to-face with a burrowing zombie-like creature, from which he flees down a side tunnel. To escape the corpse, he collapses the tunnel behind him. He then finds himself trapped in a coffin which a rat had previously emptied. Masson asphyxiates from lack of air as the rats descend upon him.