Back at Oxford, Charles and Sebastian fall into a funk. The Lady enlists Charles to watch over wayward Sebastian, but Sebastian continues his drunken revelry. A crisis is narrowly averted, while Sebastian's mood continues to grow darker.

Charles returns from his art studies in Paris and journeys to Brideshead for the 1925 New Year's celebration. Sebastian has returned from an excursion to the Levant with Mr. Samgrass, but photographs of the holiday and comments made by the two clearly indicate Sebastian frequently went off on his own to satisfy his hedonistic needs. Sebastian agrees to participate in a fox hunt although he plans to make an early escape to a pub, so he asks Charles for money and his friend acquiesces. When Sebastian returns home heavily inebriated at the end of the day, a distressed Lady Marchmain questions Charles. Learning he financed Sebastian's drinking binge, she rebukes him for enabling him, and Charles leaves Brideshead, fully expecting never to return.