Happy that Mike, her husband of 40 years, is finally retiring, "Lady" Sandra Abbott (Imelda Staunton
) is looking forward to the future. That is, until she walks in on Mike with her best friend. Shocked, the betrayed wife leaves the luxurious home she shares with her husband and takes refuge with her elder sister Bif (Celia Imrie
). Bif lives a bohemian life in an inner-city flat in London, where she keeps fit with dance classes for seniors.
In an effort to cheer Sandra up, Bif convinces her to come to a dance class. After much resistance, snobby Sandra, who was a talented dancer in her younger years, reluctantly comes along. Slowly, Sandra begins to warm up to Bif's free-spirited ways and the two sisters become closer, as Sandra learns how to be happy again.