With such a serious look on his face, he seriously expected him to guess were he'd been. He never thought to hear that, however. And it unsettles him just a bit. Enough so that he's speechless, unable to say anything until Sherlock changes the subject a wee bit. He has no idea how exactly he changes, exactly what happens, but it's become obvious no one likes his future self. "I -" He swallows, fiddles with his mug and jumps at the first subject change. "Yes. Last mission," Mycroft confirms with a shaky nod.