It's 1938 and Julia Lambert (ANNETTE BENING) is a middle-aged but still highly acclaimed London stage actress. With the help of her husband and theatrical director Michael Gosselyn (JEREMY IRONS), financier Dolly De Vries (MIRIAM MARGOLYES) and personal assistant Evie (JULIET STEVENSON), she would seem to have it all, yet she's bored with her personal and professional life, suffering from both burn-out and a midlife crisis. When her close friend Lord Charles (BRUCE GREENWOOD) cuts off any potential romance as he wants to put some distance between them to avoid any potential rumors of an affair, she turns to young Tom Fennel (SHAUN EVANS). He's an American who claims he's her biggest fan and it's not long before they are having an affair.
That new passion put some spark back into her life and she's suddenly infused with enthusiasm about mounting a new stage production. Yet, when Tom's attention turns to young actress Avice Crichton (LUCY PUNCH), Julia is thrown for a loop once again as she's fallen head over heals for him.
With ghostly or imagined advice from her long-dead theatrical mentor Jimmie Langton (MICHAEL GAMBON) and some honest talk from her adult son Roger (TOM STURRIDGE) regarding her blurred personal and stage personalities, Julia tries to get her life back on track. And when she senses that forces might be conspiring to replace her with Avice, the seasoned actress sets out to maintain the status quo as only she can.