The story follows Billy Pilgrim , an "ill-equipped" American soldier and later an optometrist, who becomes "unstuck in time" .
Billy randomly travels between his youth, his wartime capture, his mundane middle-class life, and his time as an exhibit in an alien zoo on the planet Tralfamadore .
The Tralfamadorian perspective suggests that all moments (past, present, and future) exist simultaneously and cannot be changed.