In 1926, the renowned mystery writer Agatha Christie disappeared from the world for 11 days. Based on this actual event, the film fictionalizes her whereabouts during that time. When her husband announces that he is leaving her for another woman, Christie creates a mystery out of her own life by hiding in a Harrogate hotel and plotting revenge on her spouse while all of England searches for her. The reporter who finds Christie tries to foil her plan and finally falls in love with her.