A disoriented and ill-trained American soldier named Billy Pilgrim is captured by German soldiers during the Battle of the Bulge.
Trained as a Chaplain's assistant, he arrives in Belgium just as his unit is overwhelmed by the Germans. There is not enough time to issue him with combat gear. He and other prisoners are sent far from the front to live in a makeshift prison, a disused slaughterhouse in the city of Dresden. During air raids the prisoners and their guards take shelter in a deep cellar, originally built to keep meat cool. Because of this shelter they are among the few survivors of the firestorm which consumes the city after an air raid.Billy has become "unstuck in time" for unexplained reasons (though it's hinted towards the end that his surviving a plane crash left him with mild brain damage). He meets, and is later kidnapped by, aliens from the planet Tralfamadore, who exhibit him in a Tralfamadorian zoo with Montana Wildhack, a pornographic movie star.
The Tralfamadorians see in four dimensions, the fourth dimension being time. Tralfamadorians have seen every instant of their lives already; they believe that they can't choose to change anything about their fate, but can choose to focus on any moment in their lives that they wish.Throughout the novel, Billy hops back and forth in time, reliving various occasions in his life and fantasy life; this gives him a constant sense of stage fright, as he never knows what part of his life is coming up next. He spends time on Tralfamadore; in Dresden; numbly wading through deep snow in WWII Germany before his capture; living married in America after the war; up to the moment of his murder on Earth many years later.
By the time of his murder, Billy has adopted Tralfamadorian fatalism, which has given him great personal peace; he has spread this philosophy to millions of humans and has become a popular public figure on Earth.Billy's fatalism appears to be grounded in reality (at least in the reality which Billy perceives); after noting that Billy had a copy of the Serenity Prayer in his office, the narrator says, "Among the things Billy Pilgrim could not change were the past, the present, and the future." One of his Tralfamadorian captors, who seems sympathetic to humans, says that out of 31 inhabited planets it has visited, "only on Earth is there any talk of free will.
"The book examines many events in Billy's life, including the death of his wife, his capture by the Nazis in World War II, and the infamous bombing of Dresden that was the inspiration for the book. Although the narrative of Billy's time in Dresden anchors the book, a major secondary theme is his easy and affluent life as an optometrist in the city of Illium, New York (Vonnegut's fictional stand-in for Troy, New York) which contrasts sharply with both his war experience, and with the life he knew before the war in what was post-Depression America. This also parallels Vonnegut's own transition from the dismal years of the 1930's to, as he describes.