On this level, your goal is to save the humans from the Pfhor onslaught. In order to have a chance of completing this mission successfully, you must immediately proceed to the windows that overlook the Recreation floor, and kill as many Hulks as possible before the humans are killed.
However, don't worry too much about saving the humans if you are about to be killed. The game plays no different in either case. The only difference is the message you get at the final terminal.
There are 3 secret areas on the map. The first is located in the Stem, just below the left 'leaf' on the map. There is some ammo there as well as a term.
The second secret area is hidden behind one of the 'notches' near the term and shield generator. A Magnum, as well as more ammo, can be found in the revealed corridor.
Within this corridor is the third secret area. It is located on the left-hand wall (or the bottom wall on the map), and contains a terminal message.