On October 3, 1951, the New York Giants' Bobby Thomson came to bat in the bottom of the ninth with two out, and the Dodgers leading by two runs. He pulled Ralph Branca's inside fastball into the left-field stands, abruptly winning the game, the series, and the pennant with the Shot Heard 'Round the World.

In 1992, Don DeLillo wrote about this event, and focused not on Thomson or even Branca, but on Dodgers left fielder Andy Pafko, over whose head the ball flew. "Pafko at the Wall", which became the introduction to Underworld, zooms in on Pafko just as the rest of the world ceased to notice him:

He tomahawked the pitch and the ball had topspin and dipped into the lower deck and there is Pafko at the 315 sign looking straight up with his right arm braced at the wall and a spate of paper coming down.

This shifting of focus to the unnoticed or absent is Mr. Delillo's unmistakable signature. Another example is provided by the quiet climax of "Long Tall Sally", the next section of Underworld:

I look at the Lucky Strike logotype and I think target.
I watched men in moon suits bury drums of nuclear waste and I thought of the living rocks down there, the subterrane process, the half-life, the atoms that decay to half the original number. The most common isotope of uranium is bombarded with neutrons to produce plutonium that fissions, if we can generate a verb from the energy of splitting atoms....
But the bombs were not released. I remember Klara Sax talking about the men who flew the strategic bombers as we all stood listening in the long low structure of sectioned concrete. The missiles remained in the rotary launchers. The men came back and the cities were not destroyed.

Mr. DeLillo's characters are sometimes incomplete, but this makes them more rather than less realistic: they sense their own incompleteness, and search for some means to redress it. These quests, which drive the plots of his novels, are ill-defined and may change course in midstream, like the mutating assassination plot in Libra or the intermittently homicidal Jack Gladney in White Noise. No one is more aware of this uncertainty, of the tentativeness of identity, than Mr. Delillo himself. Consider the haunting prologue to Mao II:

The thousands stand and chant. Around them in the world, people ride escalators going up and sneak secret glances at the faces coming down. People dangle teabags over hot water in white cups. Cars run silently on the autobahns, streaks of painted light. People sit at desks and stare at office walls. They smell their shirts and drop them in the hamper. People bind themselves into numbered seats and fly across time zones and high cirrus and deep night, knowing there is something they've forgotten to do.
The future belongs to crowds.