A1: As soon as you step off the elevator, three guards will be using the walls below as cover. The game will instantly go into high alert mode whether you've been spotted or not, and you will not be able to end it, no matter how many guards to take down. Even if you enter the elevator and return, the high alert will remain. Your goal is to make it to the bottom of the screen and approach the door below with card 2. Inside is a prisoner who will tell you that Dr. Pettrovich is being held in a cell underground. When you exit the room, the guards that you may have defeated will return and be waiting for you on the top side of the screen. Simply run across to the right to reach room A2.
A2: Once again, the high alert mode will continue. The only thing for you to do here is to run across the room and access the path in the lower right to reach room B2.
B2: Three soldiers will be taking cover behind the three columns in this room. Cross to the left along the top path, stopping to avoid any gun fire as you pass, then head down the left side and approach the path to room C2 below.
C2: Standard foot soldiers will be replaced with jet pack soldiers, so be on guard. There is a door along the bottom of the screen that will open with card 4. Inside, in addition to some ammo, you will find access card 5. However, be aware that a never-ending supply of soldiers will follow you into the room, so be quick about collecting the card and the ammo, and get out as quickly as possible. Once you do, continue heading right to room C3.
C3: Once again, jet pack soldiers will fly around to attack you. Activate your newly acquired card 5, and approach the door at the top. Inside will be another soldier, and more will enter from behind. Run to the elevator doors in the back and you will finally be safe. This elevator, much like the previous one, is somewhat broken; it only goes down. Ride this elevator to the basement level, and step outside.