Use the pillars to make your way to the top of the slope. Watch out for the
collapsing floor between the two pillars by the window. Immediately jump to the
taller pillar before you fall through. Shimmy across to the right and pull up.
Continue up the slope and drop into the hall and kill the guard up ahead on the
right. Proceed down the walkway and kill another guard to your left. Pull the
box at the end of the room to open the way to the Theater. Head back and jump
over the balcony.

Kill the crewman and the guard who appear below the balcony. Drop into the pit
where these bad guys used to be and move the box to reveal the Theater Key.
Push the box back to climb out and kill the boss who has just arrived. Head for
the Theater and kill the crewman who is to the right of the theater door. Enter
the theater and kill another crewman to the right unless he was already waiting
behind the door in which case; kill him where he stands.

A boss and crewman are on the right balcony so kill them and flip the switch
nearby. Then go pull the curtain on the stage and kill the workman. You may
want to light a flare to find the button across the pit of glass. Press it to flood
the pit back in the previous room where you found the Theater Key. Return to
that area, killing another boss on the way. With the pit full of water, you can
now make it across and enter the passage and exit this level...