Pnin, a refugee in his 50s from both Communist Russia and what he called the "Hitler war", came to the United States in 1940 and is an associate professor of Russian at fictional Waindell College, probably modeled on Wellesley and Cornell, where Nabokov had taught. At Waindell he has settled down to an uncertain, untenured academic life full of various tragicomic mishaps, misfortunes, and difficulties adjusting to American life and language. Characters in the book include his departmental supervisor, various professors and university staff, his landlord and wife, his ex-wife and her son, and the narrator, who is unnamed. Eventually a plot to oust him from his academic position succeeds. Pnin leaves Waindell, driving out of town with a dog as his companion.
In several earlier scenes, Pnin called the veracity of the narrator into question, and oddly, for an almost uniformly benevolent character, seems to bear malice towards him. As presented by the narrator, those outbursts seem to be no more than evidence of Pnin's quirky nature. But the final words of the book open up delirious new possibilities; they are the spoken words of yet another Pnin "observer" and they disconcertingly leave the reader with an entirely different, and crueller version of perhaps Nabokov's conclusion to the events of Chapter One. We remember that the narrator, back in Chapter One, was disappointed by the prosaically benign conclusion of those events, claiming to hate happy endings. Now a new narrator seems to have provided him with a more satisfactorily unhappy conclusion to those events. But as we only have Nabokov's by-now highly suspect testimony to vouch for the words of the new narrator, we are left to wonder if the new happily-unhappy version was ever spoken, or if Nabokov is simply editing an earlier text of his own devising with which he has grown increasingly dissatisfied. The possibility presents itself that Pnin, vanished from the University without a forwarding address and replaced by Nabokov, is no more than the novelist narrator's invention — a character for a novel. However, Pnin materializes out of the void into which he has disappeared—not in this text, but in Nabokov's later novel Pale Fire (1963).