Kurt Vonnegut wishes to write a novel about the firebombing of Dresden, which he witnessed as an American POW and survived by hiding in a slaughterhouse. Vonnegut contacts his friend Bernard O’Hare, but they cannot remember much about the bombing. They later visit Dresden and walk through the reconstructed city together.
Vonnegut begins the story of Billy Pilgrim, a man who has “come unstuck in time” and who was also captured in the Battle of the Bulge, taken prisoner by the Germans, and kept in a slaughterhouse during the Dresden bombings. Two narratives emerge: the first details Billy’s meeting of Roland Weary, an unruly fellow soldier, their farcical capture by the Germans, transfer via railcar to a POW camp, and later transfer to Dresden, a city that appears safe from Allied bombing because it has no war industry. Along the way, Weary, who has sustained foot injuries from poor shoes given him by the Germans, dies and blames Billy. Paul Lazzaro, another soldier, overhears Weary calling for vengeance against Billy and vows to kill Billy. Billy also meets Edgar Derby, a kind, middle-aged soldier who cares for him in the POW camp and is later executed for stealing a teapot from the rubble of Dresden.
In the second narrative, Billy travels through time, from his war experience to his youth to his post-war life and alien abduction. He has trained as an optometrist, married the daughter of another wealthy optometrist, and become successful in business. He and Valencia, his wife, have two children, Robert and Barbara. But in the 1960s Billy nearly dies in a plane crash in Vermont, and Valencia, coming to his aid, dies of carbon monoxide poisoning from a car wreck. After his plane crash, Billy announces he was abducted by Tralfamadorians, small, one-eyed, one-handed aliens with a peculiar philosophy of time. Tralfamadorians claim to see all events, past, present, and future, at the same time. This “four-dimensional” view of the universe informs their feelings on life, death, and fate, and Billy begins espousing these ideas publically. He later becomes a famed orator in the 1970s, and is killed by a henchman dispatched by Lazzaro, just as Lazzaro vowed in the war.
While convalescing during a mental breakdown in his last year of optometry school just after the war, Billy meets Eliot Rosewater, a fellow patient, who introduces him to the science fiction of Kilgore Trout. These books present many radical ideas about the future, time, Jesus, and history, some of which are repeated by the Tralfamadorians and by Vonnegut himself. During another hospital stay, this time after his plane crash, Billy meets Rumfoord, an historian and professor who is putting together a book on World War II but has trouble believing that Billy was really present during the firebombing of Dresden.
A barbershop quartet at Billy's 18th wedding anniversary party reminds him of the four German soldiers who stayed with the Americans in Slaughterhouse-Five. Shortly after the war ends Billy is shipped back to America. But before he goes Billy and other POWs take turns digging out and later incinerating bodies in the rubble, including the body of Edgar Derby. Vonnegut and O’Hare were also present, and in relating this story Vonnegut has managed to recall details from the war and satisfy the novel’s initial aim: to describe the horrors of Dresden’s bombings and of war generally.