One October night in the middle of the twentieth century Detective Inspector John Cheviot got into a taxi, bound for New Scotland Yard. When he stepped out it was from a horse-drawn cab, the year was 1829, and a beautiful woman was beckoning him in front of Old Scotland Yard.

There were things Cheviot remembered but couldn't use - like how to analyse fingerprints; and things he didn't know that he could have used - like how advanced his romance with Lady Flora really was. And there wasn't even time to learn, because in the midst of helping Robert Peel establish the respectability and competence of his new police force, Cheviot suddenly finds himself and his lady accused of cruel murder.