The Dark Knight’s tech master Lucius Fox is an integral part of his success in taking down villains in Gotham City, and in Chapter 7 of Batman: Arkham Knight, Fox goes out of contact.
This triggers the Friend in Need Most Wanted side mission in the game, which will have you visiting Wayne Enterprise and taking care of an old friend and foe.
Head to the Wayne Tower on Miagani Island to investigate the sudden silence from Lucius Fox. You will need to head through the elevators, which can be accessed by heading southeast from the Bank of Gotham to Wayne Tower street sign. Turn left at the parking sign and park at the central elevator.
You will now be in your Bruce Wayne ‘disguise’. Walk through the lobby and enter the office. Approach the computer and attempt to use the retinal scanner, which will not work. Lucius will then get close enough, at which time you should use the scanner again to force him to login instead.
Move into the office to find Thomas Elliot, aka Hush. He will have Lucius at gunpoint. After a brief cutscene, a prompt will appear to counter Elliot and take his weapon. Ignore this. He will eventually turn his gun towards Bruce Wayne and attempt to shoot, at which point you will need to quickly press Counter in that split second to take him out.
If you attempt to counter while he is pointing the gun at Lucis, he will succeed in shooting him; if you are too late, he will shoot Bruce Wayne, which means you will need to time the counter-attack perfectly.
A successful counter will earn you 3 WayneTech points, and will have Elliot locked up inside the Wayne Tower. You can now exit the building through any of the doors and glide to do your regular business as Batman.