This book is based upon correspondence with Dr. John H. Watson on a very special missing person case that he and Sherlock Holmes investigated. Dr. Henry Marco disappeared, according to his wife, after he supposedly build a time machine to travel into the past to change it for the better. Both Dr. Marco and Holmes and Watson change not only the past and the future, but many pasts and many futures as they follow the time trail of the mad doctor. Extensive annotations have been added by Baker Street Irregular Michael Joseph Halm, coordinator of American Mensa's scion, the Holmesian Studies Special Interest Group.