The play takes place in three bedrooms during one night and the following morning.
The cast consists of four married couples. At the beginning of the play, the oldest couple, Delia and Ernest, are getting ready to go out for a meal to celebrate their wedding anniversary; Malcolm and Kate, the youngest, are about to host a housewarming party, to which the other two couples, Jan and Nick and Susannah and Trevor (the only ones whose bedroom is not seen), have been invited.
At the last minute Nick has hurt his back and is unable to go.
The complicating factor is that Jan used to be Trevor's girlfriend, and after Susannah and Trevor have a blazing row, Susannah finds Trevor kissing Jan.
As a result Susannah leaves the party and goes to visit Delia and Ernest, whose connection with the rest of the plot is that they are Trevor's parents; she ends up sharing Delia's bed, while Ernest is forced to sleep in the spare room.
Meanwhile Trevor himself, feeling unable to go home, is also offered a bed in a spare room by Kate, but decides to go and "straighten things out" with Nick and Jan, leaving Kate waiting up for him.
Eventually Trevor and Susannah seem to be reconciled, but at the end of the play the audience might doubt whether this state of affairs will last.