What is the fine-grained topic of the following text: For Data and Geordi Laforge, it means a trip to the holodeck and 221B Baker St. With Data in the role of Holmes and Laforge as Dr. Watson, they take on a challenge from Dr. Pulaski that Data couldn't solve a genuine mystery. Only return the topic.
Data and Geordi Laforge's adventure in the roles of Holmes and Watson on the holodeck.