The entire narrative of Barry Lyndon is a meticulously detailed account of the protagonist's rise and inevitable fall, a trajectory made explicit from the outset by the narrator. After successfully marrying the Countess of Lyndon and acquiring her fortune, Barry's hubris becomes his undoing. He is openly unfaithful, spends his wife's money lavishly in a desperate bid to secure a peerage, and alienates the high society he wishes to join. His cruel and abusive treatment of his stepson, Lord Bullingdon, culminates in a public scene where Barry savagely beats the young man, making himself a social pariah.
The film's tragic turning point is the death of Barry's beloved son, Bryan. After being thrown from a horse that Barry had given him as a birthday present, the boy dies slowly, leaving both Barry and Lady Lyndon devastated. Barry descends into alcoholism, and Lady Lyndon attempts suicide. Seizing the opportunity, the now-adult Lord Bullingdon returns from exile and challenges Barry to a duel. The duel is a tense, pathetic affair held in a tithe barn. Bullingdon's pistol misfires on his turn. In a moment that can be interpreted as either redemption, pity, or a final gamble, Barry deliberately fires his pistol into the ground, sparing his stepson. Bullingdon, however, does not return the favor and, on his second turn, shoots Barry in the leg. The wound is so severe that the leg must be amputated. Defeated and broken, Barry accepts an offer of 500 guineas a year to leave England forever, never to see Lady Lyndon again. The final scene shows Lady Lyndon, years later, signing the annuity check under the watchful eye of Lord Bullingdon, who has successfully reclaimed control of his family's estate. The film concludes with the famous epilogue, stating that all these characters, with their triumphs and sorrows, are now equal in death.