OK, so maybe you shouldn't have been so eager to follow that little voice in your head. You'll just have to set things right.

You'll return from your encounter with Satan on an elevator outside a warehouse. Go through the large door and quickly possess one of the light cops patrolling the area. You may need to hide a bit until one of them is an easy target. Your first priority is to gain access to the annex.

Go through the security door into the next area. Go to the windowed office at the far end of the garage and activate the console on the left. This will open the security door to the next room. Go through the security door.

In the next room, you'll find an inactive elevator, an active elevator, and some consoles. Ignore the consoles for now and enter the elevator guarded by two light cops. Ride the elevator up to the elevator control room. Activate the console to restore power to the storage elevators. There will be a security alert, so be prepared for some conflict.

Go out through the door onto the platform. Possess the worker and active the controls near the doors. Run through while they are open. Get in the elevator and go down.

In the garage, go to the console on the wall to the left. Activate it to summon a radiation worker. When he emerges, possess him. Now, enter the storage elevator and take it up to the second floor storage area. On the opposite wall is an elevator leading to the third floor. Go up.

On the third floor, you'll see a console that engages the rad bot. Activate it, and it will descent to floor two. Get back in the elevator and go down.

On floor two, find the console and activate the rad bot again. Now, enter the other elevator and descend twice to the basement storage area. In the basement, you must engage the rad bot once again. Before you leave, activate the small lift near the elevator. This will lift a box that will give you access to the upper walkway. Up there, you'll find a rocket-propelled harpoon. Take it.

Get in the elevator that leads down to the nuclear control center. Go down. Use the console to activate the rad bot. Once the evacuation alert is signaled, ride the elevators back up to the tank garage.

Once you are in the tank garage, go through the door. The annex door will be directly across the garage and will now be unlocked. Before leaving, possess a worker and have him pick up the harpoon. Now, exit through the annex door.