Line: MORIARTY: (text message) Dear me, Mr. Holmes. Dear me…
Reference: In The Valley of Fear, Holmes receives a telegram from a sinister anonymous sender (Holmes knows it’s Moriarty) with this very message on it, just after he discovers the former Pinkerton agent tried to fake his death and hide from his pursuers. Watson laughs at the message, thinking it a joke, but Holmes knows better–and sure enough, he learns of the man’s death at sea shortly thereafter.
In the episode, it’s a modern equivalent of a telegram (a text message) sent from Moriarty to Mycroft, not Sherlock, Holmes, to inform him his plans are known and therefore foiled. No murders result from it, though there is lots of intrigue.