After using the comm terminal, open the heavy door and kill all aliens in the area. Go through the small door and up the narrow stairway to reach switch 1. Enter the corridor that has now appeared. At the end of it, jump to the room with two (initially hidden) platforms on either side and with a recharger. Once the platform on the right has lowered, make your way to the garbage crusher. Quickly climb onto the small side-elevator to the north (otherwise you get squished!). When you reach the top, use the pattern buffer.
Now you must venture on to those winding, two-level corridors. Getting to the end is quite easy, and you'll eventually find your way to the large square room to the east. Enter and kill all the aliens, then head out via the other corridor next to where you came in (there's also a handy pattern buffer nearby). Ride the large elevator downwards, and prepare for (what is reportedly!) one of the most challenging puzzles in the whole of Trojan...
Not only are there lots of monsters here, there is also a platform puzzle that requires much thought. There are 4 switches in separate rooms, with each room facing the central area where there is a set of 3 platforms (platform C, D and B). These platforms need to be lowered until they're the right height to walk across. Normally, each platform would travel all the way down into the lava. However, they can be stopped manually at the right height (hint: when the platform is in the raised position, punch the switch twice; the timing is just right for stopping the lift at the correct height). Use switch 2 (you have two choices) to set platform B, next use switch 3 to set platform C and finally use switch 4 to set platform D. Now use the bottom-right lift to get into the lift room itself. With luck, the platforms will be at the right height to walk across.
Follow the corridor around to the bottom of a large, slow-moving
lift which will take you to the centre section of the large square
room. Make sure you check the door halway round the corridor, you'll
find the pump-action shotgun, a pattern buffer, and a couple aliens
that must be killed. Hit switch 5 with a grenade to raise the
stairs and then flip switch 6 to leave the room. A door will
have opened now leading all the way back to the beginning of the
level. Eliminate the last remaining aliens. Activate the initial comm
terminal, and, assuming all aliens are dead, off you go to Can't
Be Too Careful Nowadays...