Underworld is a non-linear narrative that has many intertwined themes. A central character is Nick Shay, a waste management executive, who leads an undirected existence in late 20th-century America. His wife, Marian, is having an affair with one of his friends.
The events of the novel span from the 1950s through the 1990s. The characters in the book respond to several historical events, including the Cuban Missile Crisis and nuclear proliferation.
The novel is divided into eight sections:
- Prologue – The Triumph of Death (3 October 1951; this section has been published separately, as a novella, under the title Pafko at the Wall)
- Part 1 – Long Tall Sally (Spring-Summer 1992)
- Part 2 – Elegy for Left Hand Alone (Mid-1980s – Early 1990s)
- Part 3 – The Cloud of Unknowing (Spring 1978)
- Part 4 – Cocksucker Blues (Summer 1974)
- Part 5 – Better Things for Better Living Through Chemistry (Selected Fragments Public and Private in the 1950s and 1960s)
- Part 6 – Arrangement in Gray and Black (Fall 1951 – Summer 1952)
- Epilogue – Das Kapital
DeLillo said that the novel's title came to him as he thought about radioactive waste buried deep underground and about Pluto, god of death. The waste and byproducts of history, dissected and discussed throughout the novel, constantly resurface from the underworld (or, subconscious) of the American population despite their best attempts to repress and bury things they would rather forget. Further connections and connotations about the title can be made between part of the novel's subject matter (mafia criminals in New York who Nick Shay fantasizes may have had his father killed), and the 1927 gangster film of the same name.