The Baker Street Irregulars are back on the case as master detective Sherlock Holmes sets an elaborate trap to capture the wicked Professor Moriarty and dismantle his criminal organization, at last! But Moriarty has his own plans. In their final adventure, the Irregulars face the greatest challenge of their careers. The quest will take them, for the first time, out of England and on a thrilling chase across Continental Europe. Will Holmes and the Irregulars succeed or fall prey to the most dangerous man in all of England?