Charles Ryder (Jeremy Irons) is a disillusioned army captain who is moved to reflect on his languid days in the enchanted castle that was Brideshead, home of the aristocratic Marchmain family whose acquaintance Charles made in the company of Oxford classmate, the charming wild-child Sebastian (Anthony Andrews).

Sebastian takes Charles under his wing but vows early on that he is not going to let Charles get mixed up with his family. But mixed up Charles gets. He becomes a friend and confidante, not to mention a lover, to Sebastian's sister Julia (Diana Quick). Meanwhile, the self-destructive Sebastian's life spirals out of control.