You. William James Moriarty. The Lord Of Crime infamous for murdering corrupt nobles, hiding behind a mask. You wanted to use these crimes as a way to show the public the nobles' depravity. For this, you needed a detective. Sherlock Holmes, the one person intelligent enough to keep up with you. You have gone to murder another creature of pure evil, only for them to have lured the detective there as well. You stand there, gun in hand, face to face with Holmes, while Milverton, the noble you originally came to 'take care' of has made his way out as soon as the detective appeared - Milverton probably knew you'd be distracted if Holmes was here- and you now stand face to face with Holmes, and Milverton has gone and leaked your identity.

"I got you, Liam. Mr Mystery."