Paul Berlin, a young mid-westerner drafted into the Vietnam War in the late 1960's, deals with the psychological trauma of the war by concocting a series of surrealist fantasies surrounding a chase after Cacciato, a soldier in his squad who has gone AWOL. Paul is a coward. He believes this about himself, and every action he takes seems to reaffirm this belief. We first meet Paul and his platoon after a series of horrific, and senseless, deaths have taken their toll on the platoon's mental, emotional, and moral strength. They are depleted. One soldier died of fright. One stepped on a landmine. Another is killed searching a worthless tunnel, and his buddy is killed going after him into that same tunnel. All of these deaths appear to serve no greater purpose. They are in a nightmare of death and suffering, and everyone is just waiting until it's time to go home again.
Cacciato is the only one seemingly untouched by all this trauma. The platoon sees him as a naive simpleton at best, a dangerous idiot at worst. But whatever the truth, Cacciato's sunny disposition remains outwardly unruffled by all the death around him.
Then Cacciato goes AWOL.
The plot of the book is bracketed by the same event: a squad, including Paul Berlin, is assembled and sent after Cacciato. They track him down to a hilltop on the border of Laos. As they move in, Paul is terrified. He soils himself and huddles in a ditch. There is an explosion, some gunfire....
And this is where the storylines diverge. Paul knows the truth (if the reader doesn't quite realize this yet). He knows that the hardened, morally-numbed squad (which also fragged their own lieutenant for refusing to alter the ridiculous policy of searching every single booby-trapped tunnel) has killed Cacciato. He knows this, and yet he allows himself to believe that Cacciato has somehow escaped -- that in the confusion he made it across the border into Laos. Cacciato often spoke about how easy it would be to just start walking in the direction of Paris and leave the war behind. Simple as that. Paul allows himself to believe that this is precisely what Cacciato has done, and furthermore, he allows himself to believe that the squad has been tasked with chasing after him, no matter where that chase leads.
So begins the fanciful chase that takes them across Laos and into Burma, and on and on, from India to Iran to Germany and finally to Paris, with surrealist adventure after adventure piling up behind them, each one more surreal than the last and each further unraveling the legitimacy of any of this chase having actually occurred in reality. The closer they get to "Paris" (or in other words, the farther they get from Vietnam), the soldiers act more and more like civilians, forgetting the conditioning that turned them into drafted automatons in the first place. The final episode in Paris is a mock playing out of the Paris Peace Conference, via the internal struggle that goes on in every conflicted soldier's mind: Is my fear of the war stronger than my fear of deserting and being seen as a coward?
At this point, before a "decision" can be made, Paul is yanked back to reality. We are back at the moment right before the squad ascends the hilltop on the Laotian border, with Paul huddling in his own cowardly excretions, and this time there is little ambiguity of what the final outcome for Cacciato really is.
Throughout the book, a third thread weaves itself between the past, "real" horrors" and the abstract escapism of the Paris chase: the "Observation Post" chapters. In these, which presumably are the most "real", take place long after Cacciato has been dealt with, and are simply Paul pulling guard duty in isolated observation posts throughout the Vietnamese countryside. He stares out into the hostile, moonlit landscapes and muses on his situation, the decisions he's made, and what those decisions say about him as a human being. In essence, it becomes clear (so far as anything is clear in this book) that the entire Paris chase is Paul's attempt to work through whatever thought process drove Cacciato to desert. Paul realizes that ultimately he is too much of a coward to run.
Best part of story, including ending:
The treatment of the Vietnam War as a particularly surreal or nightmarish landscape is not new -- ("Apocalypse Now", "Full Metal Jacket", as well as O'Brien's own "The Things They Carried" all take this as a given) -- but this story weaves that surrealism into the very narrative structure in a way that is far more effective and unsettling.
Best scene in story:
The scene where we first meet Cacciato as he is happily fishing in the muddy (fish-less) craters where a B-52 dropped its bombs perfectly encapsulates Cacciato's quirks and the greater absurdity of the war itself.
Opinion about the main character:
Paul's cowardice feels so real, so pathetic and genuine, that you can't help but come to understand how that cowardice might be the only rational response to his situation.