Although this story is billed as a Willow King mystery, it actually features Emma, her friend at university, as she blossoms both personally and professionally. From a well-to-do and snobbish family, Emma has shocked everyone by choosing criminology as her field of study. Emma has faced her share of discrimination at St. Albans; she “had long ago modified her accent, flung her velvet hairbands in the bin, and never talked to anyone about the life she had lived in Gloucestershire, but it was becoming very clear that she had not yet done nearly enough to placate her colleagues.”

In short, Emma needs to prove herself, both to her fellow students and professors, and also to herself. A research project on the subject of polygraph tests provides just the thing for Emma -- and of course a suitable plot for a mystery.

Willow King is the middle-aged friend and sometime sleuth who has befriended Emma. Willow was a civil servant who made a good deal of money publishing romance novels under a pseudonym. Now married to a police superintendent and the mother of a young daughter, Willow still can’t resist her urge to play detective. Through a friend at the newspaper, she brings the case of Andrew Lutterworth to Emma’s attention. It seems that Lutterworth is serving a sentence for a fatal hit-and-run accident from several years past. His wife Jemima is convinced that he is innocent and confessed to the police only under duress. Convicted by circumstantial evidence, he is currently imprisoned and, after some coaxing, willing to become a subject of Emma’s lie detector tests.

The point of view alternates between Emma and Willow as the two begin their investigation of Andrew Lutterworth’s conviction. Along the way they get the help of two young men, both with a romantic interest in Emma. First is her friend from university, Jag. A native New Zealander, Jag is large and imposing in his leather motorcycle gear. He is the epitome of what Emma’s family would not want her to marry. Then there is the charming newspaper reporter Hal Marstall. Helpful as he is to Emma’s research, she has been warned away from him because of his reputation as a womanizer. Her relationship with these two men, and her detested brother Anthony, help to illustrate Emma’s growing maturity and her ability to move from the shy and quiet young girl to an assertive and capable young woman.

Still, it is the strong and determined Willow who seems to make things happen in the crime investigation, much to her husband’s displeasure. As she delves into the night of Lutterworth’s hit-and-run accident, she discovers that he may indeed be innocent of the crime. Why then did he confess to police? Emma is also confused upon meeting Lutterworth. His polygraph responses make no sense to her. What could he be hiding?

Natasha Cooper blends a suitable variety of characters with an unusual crime to create a satisfying whodunit. For fans of the British cozy mystery, Willow and Emma won’t disappoint. (There are plenty of hot baths, hot tea and dearest friends.) And for fans of a just plain good story, Lutterworth’s subtle and creepy demeanor will keep you reading too. Last but not least, for readers who enjoy a strong female detective, Sour Grapes provides both a veteran and a likable up-and-comer to enjoy.

--Martha Moore