Just before Christmas, Sydney Opera House usherette Sharon and her friend Eva meet best mates Brendan and Tony in the midst of an anti-war protest in front of two United States Navy ships. Despite being dressed as Santa Claus, the men chat up the women. Brendan attempts to impress Sharon by claiming to be a singer who has performed at the Opera House. The four go on a double date to see Midnight Oil and later the women kick the men out of their flat after overhearing them (falsely) claim to each other to have seduced their dates. There are news reports of growing tension between the United States and Soviet Union with fears that one mistake could lead to nuclear war.
On New Year's Eve, Sharon is working at the Opera House and after the performance Eva meets her so they can go to a party. They find Sam asleep in one of the theatres. Sam is a US Navy sailor who, having known for months that war was imminent, deserted his ship and has been hiding in the Opera House. Sharon recognises him from a newspaper article which describes him as "missing". While the three talk in the control room of the theatre, Brendan comes onto the stage and attempts to sing. It turns out he is a cleaner there. While the women talk to Brendan, Sam overhears on the radio that war has broken out in Europe and tactical nuclear weapons have been used in Germany. There are further news reports that four military targets in Australia - North West Cape, Pine Gap, Nurrungar and Jervis Bay - have been attacked with nuclear weapons.
Ordered to stay in the Opera House, the four try to figure out the best way they can survive the escalating conflict, initially hiding in the basement then going to a bar (for which Brendan has they key), getting drunk and playing strip poker. Through a series of flashbacks and talking about their past, the four begin to bond. Brendan and Sharon pair off and have sex in a storage room, and Eva finds a television and learns that the war in Europe has escalated to a full-scale nuclear exchange, and much of Europe and the United States have been devastated. The newscast then shows footage of horribly burned and disfigured victims of a nuclear blast near New York City. As the sky begins to turn red from firestorms around Sydney and air raid sirens go off, the four, upon hearing an emergency announcement on the radio, join thousands of others taking refuge in the underground Martin Place railway station. As Sharon and Eva sing "It Might as Well Rain Until September" to entertain the crowd, the lights go out and a loud explosion is heard above them.
Richard Mason and John Duigan brought the script to Hoyts Edgley who agreed to back it. Simon Wincer called Duigan "a highly talented filmmaker and a brilliant writer" who was "an utter joy to work with".
The Opera House was only used for ten days of filming because it was too expensive to hire. The rest of the movie was shot in the Seymour Centre.
The film includes a performance by Midnight Oil.
Paul Hester, drummer for Split Enz and Crowded House appears in the film uncredited.
One Night Stand grossed $111,978 at the box office in Australia, which is equivalent to $284,424 in 2009 dollars.