Jess Harper's life is turned upside down when her twin sister disappears a week before rehearsals are due to start for a new West End musical in which Lora has the lead role. Jess decides to impersonate her in order to save her career, despite her initial dislike of Kyle Drummond, the determined and arrogant director. The last thing she expects is the irresistible magnetism that draws them together, but there's also evidence Kyle dated Lora. Is Jess simply a substitute, in real life as well as in the show? And what will happen when Lora eventually returns?