Alistair and Miles, both with aristocratic connections, start their first year at Oxford University. Though they are very different — Miles is down to earth and happy to have a girlfriend from a lower background, Lauren, whilst Alistair is a snob with aspirations to follow his uncle, a Tory MP — the common bond is that they both become members of the Riot Club, a long established elite drinking club priding itself on hedonism and the belief that money can buy anything.
Alistair takes the club in more of a competitive way and ends up loathing Miles. Having been barred from most establishments in Oxford, they have their annual dinner at the function room in a country pub, where their rowdy behaviour angers other patrons though they reimburse Chris, the landlord. After hiring a prostitute who refuses to perform group oral sex, Alistair takes Miles' phone and texts Lauren without Miles knowing, whom they importune to Miles' horror. Getting progressively more drunk and ingesting drugs, they start to trash the room, and when Chris comes to complain, Alistair savagely assaults him, landing him in hospital. Though shocked, none of the others do anything to stop him except Miles, who rings for an ambulance.
The boys are all arrested but believing that the club is more important than the individual, they agree not to give statements and go on to suggest that Miles, as the newest club member, should take the blame for the attack on Chris. Alistair's skin is then found underneath Chris' fingernails, meaning they can arrest and charge him. Miles' now-ex girlfriend refuses to talk to him, and Miles is approached by the new president of the Riot Club (Guy Bellingfield) where he decides to leave the club.