Patricia Wentworth began writing crime novels in 1923 with the debut of The Astonishing Adventure of Jane Smith. It was an auspicious beginning to a 40-year career during the era known as the Golden Age of mystery writing. 

Jane is broke, she's just lost her job and her landlady has kicked her out. When an amorous young man approaches her on a park bench it soon becomes clear that he has mistaken her for her cousin Renata. Their mothers were identical twins and even though Jane has never met her, Renata's fiance insists they too are identical. He's desperate. 

It seems Renata sleepwalked into a meeting of her father's friends and overheard their criminal plans. She's lied about hearing anything but they doubt her story and are holding her prisoner. The plan is that Jane switch places so he can get his love to safety. 

Jane's only other option is the workhouse, and being a plucky young woman ripe for adventure, she agrees. But she's no fool and informs a former beau who works at Scotland Yard of the scheme. Henry March is appalled but agrees to be her outside contact in case of trouble. Her first challenge turns out to be hiding her natural intelligence while impersonating the somewhat dim Renata. 

All the ingredients of an English mystery novel are in place: a country mansion with hidden panels, laboratories and caves; dastardly villains bent on destroying civilization; a daring, clever girl determined to unravel the conspiracy; and not one, but two budding romances. 

Written during the decade in which women gained the vote, Jane Smith is a heroine of her time. Far from waiting for the hero to come save her, Jane is determined to solve the mystery before Henry does!