"I'm not your messenger," Sherlock points out just as two burly men give him looks. You need to leave now looks. Sherlock frowns lightly before he turns on his heels. "I'll have John ring you when I've cracked it."

Oh, but that's not what Sherlock wants to do, not really. He wants to use whichever poor soul is 'Y' to get another chance at Moriarty. Maybe sit down to tea.

That thought it more humorous to the usually stoic Sherlock than it ought to be.