When Mycroft received a panicked call from John, he was only told that Sherlock had been attacked, but much like Sherlock, he's well versed in reading people and he knew that the tone in the doctor's voice was definitely not good. He's always secretly feared the game that Moriarty and Sherlock play against each other, knowing that Moriarty has the capability of getting into Sherlock's head the way no one else can. He's attempted to stop the consulting criminal on his own without Sherlock knowing, but all attempts thus far have been futile, the criminal managing to slip through his fingers each time.
Though he doesn't yet know the extent of the damage, Mycroft silently vows to eliminate Moriarty once and for all, the manner in which to be determined based on how bad the attack was, how much he's managed to damage his little brother.
Though everyone knows Mycroft's ability to make people disappear, it isn't talked about, which is probably for the better. Though most of the time he allows the person to simply end up lost in the system, there are times where more extreme measures have to be taken, whether it be for information he required, or to settle an unfavorable score. Though the latter of the two is rare, it has mostly revolved around Sherlock, and Mycroft's never ending battle to keep his brother safe, without him particularly knowing about it. While Sherlock is clever and fully capable of deducing just about anything, it has been proven time and again that Mycroft is on a level slightly higher than the younger man, and therefore capable of getting rid of some unsavory characters in Sherlock's life that have chosen to assist him on paths that weren't particularly favorable. The amount of drug dealers in London seem to be at an all-time low.
While Mycroft organizes a flight back to London, he also sends a team out to locate Moriarty with orders to bring him back alive, this being one of the few times Mycroft is willing to get his own hands dirty.
When he gets an update from John on the extent of damage that was inflicted on his little brother, complete with the attachment containing pictures, Mycroft suddenly stops his steady pace from his town car to the plane, Anthea so caught up in her phone that she almost runs into him.
She glances at him for only a split second before returning her concentration back to her phone, but after another moment she finds herself staring at Mycroft, her usually unshakeable boss staring at his own phone with the color drained from his face, and almost a completely indiscernible tremor to his hand.
"Sir-"
"Find him, now."
Though he cuts Anthea off to say it, his words are meant for everyone within hearing range, the color returning to his face as he suddenly closes the gap between himself and the plane, Anthea trying to keep up as he boards it and instructs the pilot to not waste any time.
Though she's tempted to ask him what's going on, Anthea knows better, instead acting like she's focusing on her phone while silently peering over the device at her boss. In all the years that she has worked for him, there have been very few times in which he has shown any personal emotion, where he's made anyone believe that he cares. Even the few times it has happened, it has never been to an extent such as this, Mycroft staring out the plane window with the grip on his phone so tight that it just might shatter.
About this current situation she knows two things for sure: first, the obvious, that Moriarty is involved. Second, and less obvious, that Sherlock is involved. Though he has yet to make mention of his younger brother in regards to his current state, Anthea is perhaps the only person who has been around Mycroft long and close enough to know how to read his silent cues and reactions. In those very few times that Mycroft has let his ability to care slip enough for her to see it, each time it involved the younger Holmes. The first time Sherlock overdosed, really overdosed to the point of being in hospital for a week, the fight to hide the emotion was a constant battle being fought that could only be seen by those who knew Mycroft best, and the only other person besides Anthea who knew Mycroft best was laid up in a hospital bed, unconscious for three days.
Since then Mycroft has learned to hide it better, but while she isn't as brilliant as either of the Holmes men, Anthea is smart enough to read the emotions of a man who otherwise seems impenetrable to the human side of caring when it comes to anything but Sherlock. It is with this information that she knows that when Mycroft demands that Moriarty be brought to him, she knows that the game is no longer just a cat and mouse back and forth between the two men, this time Moriarty has done something to absolutely cross the line of antagonization, and has managed to find himself right in the crosshairs of the one man in the country that will not only tear him down, but everything he may hold dear, everything he is, everything he ever was. When Mycroft gets a hold of Moriarty, the look in his eyes will take on a very physical shape, and Anthea knows that anyone around when it happens will be lucky to get out alive.
Next chapter: Mycroft makes it to Sherlock