In the early 1960s, folk singer Llewyn Davis is trying to make a name for himself in the New York City music scene. He's broke most of the time, doesn't have a place to live - he usually crashes on a friend's couch - and is having trouble booking gigs. His agent doesn't seem to be promoting his last album and he contemplates returning to his old job as a merchant seaman. For Llewyn however, life seems to just repeat itself.
Bob Hughes is the leader of a "family" of drug addicts consisting of his wife, Dianne, and another couple who feed their habit by robbing drug stores as they travel across the country.
In 1973, 15-year-old William Miller's unabashed love of music and aspiration to become a rock journalist lands him an assignment from Rolling Stone magazine to interview and tour with the up-and-coming band Stillwater—fronted by lead guitar Russell Hammond, and lead singer Jeff Bebe.
In early-1970s Las Vegas, low-level mobster Sam "Ace" Rothstein gets tapped by his bosses to head the Tangiers Casino. At first, he's a great success in the job, but over the years, problems with his loose-cannon enforcer Nicky Santoro, his ex-hustler wife Ginger, her con-artist ex Lester Diamond and a handful of corrupt politicians put Sam in ever-increasing danger.
In Greenwich Village in the early 1960s, gifted but volatile folk musician Llewyn Davis struggles with money, relationships, and his uncertain future following the suicide of his singing partner.
Former college friends meet up for a reunion that leads them to face the apparent disillusionment that defines their lives. After a week of excessive drug and alcohol abuse, events lead them to contemplate fulfilling a self destructive pact they made when they were young.