A young shipworker from Liverpool named Jude leaves his girlfriend Molly to go to America and find his father. In America, he meets Max, student at Princeton. They become friends, and Max invites him back to his house when Jude meets Max's sister Lucy, whose boyfriend was recently killed in the Vietnam war. Max, Jude, and Lucy all move to New York, where they meet Sadie, a performer, and Prudence, a bisexual high school cheerleader who ran away from her abusive boyfriend in Ohio. Lucy and Jude develop feelings for each other and eventually fall in love. Jude, Max, Lucy, Sadie, and Jojo, a guitar player whose younger brother was killed in a riot attend a party where they drink punch laced with LSD. Under the effects of the drug, they imagine a physchodelic journey where they travel across the country and see a strange circus performance, which Prudence has joined. When they all return to reality, Max is drafted to the war, and Lucy becomes concerned about him. She joins Paco, an anti-war protest leader, in rallying against the Vietnam War. Jude becomes suspicious that Paco is trying to seduce Lucy and Lucy is offended. Later, Jude bursts into Paco's office, pointing out Paco's hypocrisy. Lucy is upset by his actions and they break up. Later, Jude is arrested and beaten at a riot. His father, Wes Huber tries to prove Jude is his son, but he can't and Jude is sent back to Liverpool, as he was not an American citizen. Meanwhile, Max is injured in the war and taken back to America. He relies on morphine and it alters his mind, until he recovers. Lucy visits him daily. Back in Liverpool, Jude sees Molly, who is now pregnant by Jude's friend Phil Scully. He sees in the newspaper that rioters where killed by their own bombs, and is concerned that Lucy is dead. He returns to America where he sees Sadie's band, now including Prudence, performing on the rooptop. He joins them and sings "All You Need Is Love". Lucy recognizes his voice, runs to a builing top across the street, and Jude and Lucy see each other, smiling.