First of all, Marcus Pottermack was not his real name. But Mr. "Pottermack" thought he had excellent reasons to adopt it and to murder James Lewson, bank-manager, blackmailer and among the most loathsome characters in all detective fiction.

The tension mounts rapidly in this "inverted" detective story - one of the earliest full-length examples, and still one of the best. Characteristically, we are quickly acquainted with the perpetrator's identity: to figure out "whodunit" is not the task set readers of inverted mysteries. They face a challenge many consider far more interesting: to deduce precisely how the detective will fasten upon the culprit despite scanty or seemingly nonexistent evidence.

In Mr. Pottermack's Oversight the obstacles are formidable, for the brilliant criminal has made his victim appear to have vanished into thin air while strolling in the country. Indeed, the ingenious Mr. Pottermack seems to have anticipated everything that might thwart his plan - except that his adversary would be Dr. John Thorndyke, England's renowned expert in medical jurisprudence, admired for nearly 80 years by mystery connoisseurs as the greatest of all scientific detectives.

Whether or not you can match Dr. Thorndyke's penetrating insight - the clues are all placed fairly before the reader - you will be fascinated as you witness a virtuoso performance by a first-class scientific mind. And, equally absorbing, you will be drawn into the guilt-racked mind of a murderer as you watch ruthless determination attempting to fight off a growing sense of horror.