Geordi summons Data to the holodeck, where they travel back to Victorian London to solve one of Sherlock Holmes's mysteries. But the trip turns out to be a brief one because Data can solve the crime with very little effort. Dr. Kate Pulaski challenges Data to solve a real crime, a la Sherlock Holmes. Geordi orders the computer to present Data with an original mystery and an opponent who could defeat him. Kate joins Data and Geordi as they return to London, via the holodeck. But their game turns serious when Kate is kidnapped by Holmes' arch-enemy, Professor James Moriarty. Although they track down Kate's location, they are unable to retrieve her because Moriarty has taken control of the holodeck computer.
