16-year-old Elgin Marble has had enough of a world that is decidedly vertical. When his father, an upstanding elevator man, is marked for disposal, Elgin joins an underground group called the Crabs. This illicit group tirelessly digs tunnels in the hope of one day breaking through to the outside. But who are the Crabs, and can they be trusted? Elgin's mother, Ellen, is worried sick about her son. The ruthless school principal, Mr. Orion, warns her that Elgin is in big trouble and blackmails her for sexual favors. Together they go underground to search for the boy. Meanwhile, agents of the IVT (Institute for Vertical Thinking) are also hot on his trail, and the Crabs are feeling the heat.