When American journalist Benjamin Barrett is sent to Constantinople to report on the sea trials of a new submarine, the assignment soon becomes more eventful than he had predicted: the submarine explodes in front of his eyes; he aids a certain Professor when the latter is attacked by a gang of toughs; and he is arrested for the murder of a British spy. However, the Professor comes to his aid, and arranges for his official ‘death’ and transport to London. Moriarty makes him a proposition: to repay his debt, he will work for him for two years, and aid him in the business he has been engaged on by the Russian government. There is a mysterious masked agent—Trepoff—seeking to sow anarchy and destruction, and Moriarty must track him down and prevent a catastrophic attack at the highest echelons of British society, if only Sherlock Holmes will stop meddling in his affairs…