Stuck in a dead end town, the kids relieve the boredom with visits to the dancehall. Travolta meets another dancer to match his skills at the disco, and together they rule the floor. But both want to move on to better things, and gradually, they realise they can help eachother.
Saturday Night Fever' has become something of a joke - a kitsch touchstone for nostalgia TV and '70s club nights - but John Badham's film deserves better than that.
Away from the flashing lights of the discotheque, this is dark stuff, littered with racism, violence, date rape and salty dialogue ('If you're as good in bed as you are on the dancefloor, you must be one lousy fuck'). Lose the dancing, and you could be forgiven for thinking you were watching a Ken Loach movie.
At the heart of all this seediness is John Travolta's Tony. An angry young man in the tradition of '50s melodrama or '60s kitchen sink, he is nasty, dumb, insecure and utterly compelling. Badham shoots him like an icon from frame one - the legendary strut along the Brooklyn street, paint can in hand - so we're hooked on his charisma before he's revealed as a shop assistant in a neighbourhood hardware store.
Throughout the film, loser beats work in counterpoint with movie star moments: the smack on the head from his old man comes right after a sequence in which Tony styles his hair, clad only in skimpy black briefs and his own narcissism.
Travolta is mesmerising in every scene, carrying the film despite some woeful performances from the supporting cast. Naturally, his dancing is etched on the culture's collective consciousness, but it was the dramatic work which earned him an Oscar nomination (criminally, he lost out to Richard Dreyfuss' showy wiseass in The Goodbye Girl).
Perversely, it's the musical sequences that have failed to stand the test of time. Even if you ignore two decades' worth of parodies and pastiches, the heavily choreographed shapes J.T. and the rest throw verge on the ridiculous.
To borrow from a later Bee Gees hit, the fact that 'Saturday Night Fever' is remembered only for the disco action is a real tragedy.
Only the dancing has dated in this classic, but Travolta's sense of helplessness and despair is easily translated to modern America in this criminally underrated performance.