Your prompt is: G-man behind the scenes. That is, at his Employers', or in some way plotting—including some indication of WHAT he is plotting, even if it's just a hint or a minor component of whatever his plan is. Art or fic, it doesn't matter.
"Our assets are secure once more. The arrival of the vortigaunt team was unfortunate, true, but not ultimately damaging. I was able to deliver your message to Ms. Vance while they were otherwise occupied, which Mr. Freeman was, at the moment, unable to stop. Events are in motion as you planned, sir, as I am sure you have already learned. The Citadel has fallen, the superportal has been closed, and possibly most importantly, Mr. Vance has fallen to your wayward brother. All is progressing as it should.
"I have, however, uncovered something... worrying. Mr. Freeman is progressing faster than expected, though the vortigaunts do not yet seem to have realized it. I hindered their awareness of his potential as much as I could, so they should have no knowledge of it for several more weeks, and possibly some time past that, but... Mr. Freeman may be unlocking his potential without their help, which I am powerless to stop. Even with a complete lack of training and no experience with shaping the Vort, he has managed to render useless my Suggestions, though he has not learned to extend those skills to Ms. Vance. This makes him, as you know, very dangerous; if we do not bring him under our control before he gains control of his powers, he could disrupt your plans greatly.
"Sir, if I may be frank... Mr. Freeman frightens me. Never before have I seen such capabilities manifest in an untrained human. Even your training, competent as you are, takes years to unlock our capabilities, and even then they are usable only weakly and with great concentration. He has started to use them unconsciously and powerfully, stymieing even my abilities. While he is, for the moment, working to complete our plans, if he learned of my real purpose, or that you existed... I know him, and he would oppose us with all his skills.
"Let me be clear, sir. Mr. Freeman will, if trained, be able to access the Vort in ways far past that of most vortigaunts. I have little doubt that even you, despite centuries of training and more natural talent than even your species usually possesses, will have less power than he will after just a few weeks under an inferior trainer.
"Our time, therefore, is limited. Within the next four weeks, we must bring our plans to fruition, disable Mr. Freeman, or continue to keep the vortigaunts from realizing his potential. Despite all of my talents in foreknowledge, despite everything I have learned... if he is trained by a vortigaunt, we must prepare. Even I cannot foresee all of the consequences.
"Now, if you will excuse me, sir, I must go resume my vigil over him. It would not do to have my veil pierced by the vortigaunt team while I am unable to tend it."
The world shifted around him as the Vort bent to his will, and he appeared in a small, dimly-lit room. Gordon was curled up around Alyx on a small cot in the corner, his environment suit and weapons stowed neatly in the corner. The G-man walked silently to the edge of the cot and planted a Suggestion in Alyx, who turned over and smiled sleepily.
"Rise and shine, Mr. Freeman..." she said teasingly. Gordon responded with a jerk, nearly tossing her out of the bed as he groped for his crowbar, and the G-man, who had already retreated to the Vort, smiled humorlessly. He was confident in his ability to manipulate the physicist as long as he had control of the girl, but managing to keep that control as Mr. Freeman grew into his capabilities would be the first real test of his talents in many years. He watched from the Vort as Ms. Vance soothed Mr. Freeman and they began to prepare for the next step in the resistance.
His voice was barely a murmur as he maintained his vigil.
"Rise and shine, indeed..."
