Imagine Downton Abbey set Down Under in 1972 and you've got the gist of this handsome, if patchy, rendering of Patrick White's story of manipulation and dysfunction among the rich and selfish.
Charlotte Rampling is Elizabeth Hunter (Rampling), a difficult, bed-ridden moneybags counting down her last days at her stately Sydney home tended by two nurses, a housekeeper and her trusty solicitor (John Gaden).
The whiff of inheritance sees the return of her estranged children who both made their names in Europe. Direct from the West End comes the effete rogue Sir Basil (Rush), whose best performances are behind him - both on stage, and in the bedroom.
Following the end of her marriage to a French prince, his sister Dorothy (Davis) has fallen on similarly hard times. Yet appearances must be maintained.
Everybody knows why everybody else is here. But as they all play the waiting game, family and servants alike are surrounded by reminders of the past. Basil's is full of regret. Dorothy's is one to forget. But Elizabeth never felt more alive than the time she was caught in a raging tropical storm.
As the titular key to the story, frequent flashbacks take us back to the latter time and again. Yet it's in the here-and-now of 1972 that the film engages most.
While director Schepisi astutely captures an era full of tacky decadence but precious little elegance, screenwriter Judy Morris ladles on the indiscretions and indignities like so much sour milk.
Dorothy is dealt her fair share of humiliation but it's Basil's ego that takes the fiercest battering, whether it's from the day nurse who wraps him round her finger (played by Schepisi's daughter Alexandra), or from his own mother... although she's merely taking her lead from the London critics.
"They thought enough of me there to give me a knighthood" sniffs Basil.
"That was before your King Lear," observes Elizabeth.
Such pithy exchanges abound. Alas, the aloofness of the characters means they rarely strike an emotional chord. Which won't matter a jot to the Downton and Best Exotic Marigold Hotel crowd who are splendidly served by both cast and production team.
A classy show, but in keeping with Schepisi's penchant for food metaphors, not always as tempting as it looks.