Billy travels in time to Spring 1948, when he lies in a ward for nonviolent mental patients in a V.A. hospital in Lake Placid, New York.
The birds are singing outside his window: "Poo-tee-weet?"
Billy has committed himself to the hospital because of a breakdown in his final year at the Ilium School of Optometry.
His doctors think he's going crazy because Billy's father had thrown him into the deep end of the Y.M.C.A. swimming pool and then taken him to the rim of the Grand Canyon. It can't be because of the war.
The man next to Bill is a former infantry captain and current drunk, Eliot Rosewater.
Rosewater introduces Billy to science fiction, specifically the works of (fictional) author Kilgore Trout.
Science fiction becomes the only thing Billy can read, and Kilgore Trout his favorite author.
Both Rosewater and Billy find life meaningless because of experiences they have had in the war. They're trying to reinvent their universes, and science fiction helps.