MARIA. All over the world, at various crime scenes, the name MARIA has been scrawled on the mirrors. And now she's moved on to London.
Tuesday, Mycroft receives three photographs in the mail. Each have the word MARIA scrawled on them in lipstick. One photo of him, one of Moriarty and one of Sherlock.One week later, the name MARIA is written on the mirror of an alleged thief. It's up to Sherlock to decipher this code, and figure out just who, or what, MARIA is.