Cambridge, 1898. When the unidentified body of a young woman is found floating in the River Cam, journalist Patrick O'Sullivan calls on one woman he is sure will solve the mystery: Mrs Vanessa Weatherburn. Vanessa agrees to take up the challenge, but, with a victim as well as a murderer to identify, she knows it will be no easy task. Luckily, help is at hand; aided by her friends at Heffer's bookshop and the cream of Cambridge's academic community, Vanessa goes undercover to continue her investigation. Employing all her skills to reel in the killer, Vanessa can only hope it will be enough to solve the riddle of the river.