What do you do when you're told you've got terminal cancer at 50? Take up crochet, convert to religion and bow out gracefully? Or ditch your husband of 20 years, abandon your demanding kids, leave your job, desert your bossy mother, cash in your savings and take your two sisters on a luxury cruise?

Ruby has always been the generous mediator among her friends, family and colleagues, which is why they have all turned up to celebrate her 50th birthday. But after a few too many glasses of champers, Ruby’s speech doesn't exactly go to plan. Instead of delivering the witty and warm words her guests are expecting, Ruby takes her moment in the spotlight to reveal what she really thinks of every one of them. She also accuses her husband, Harry, of having an affair.

Saving the best till last, Ruby lambasts her octogenarian mother for a lifetime of playing her three daughters against each other. It's blisteringly brutal. As the stunned gathering gawks at Ruby, the birthday girl concludes her bravura monologue with the throwaway comment that she has terminal cancer. She has cashed in her life savings and plans on taking her two sisters cruising into the sunset for a dose of Husband Replacement Therapy. Courageous? Or ruthlessly selfish?

But do they even want to go with her now that she's cast herself off into social Siberia?