When David Melling asks his wife what she would like for her 40th birthday, the answer shocks them both. Anna wants his permission to sleep with other men. Despite juggling motherhood, marriage and a fraught job as manageress of a dress shop in the UK's largest shopping mall, Anna feels something is missing. But when David, her controlling solicitor husband, gives Anna what she wants, she is stunned. After a couple of hilarious dates, shenanigans in the shopping mall and some serious meddling by Susie, Anna's best friend, life begins to get very complicated. Will Anna's crazy idea let her recapture the heady days of her youth or destroy the very things she cares about most - her children, her husband and her job?