After you get into the room with the cooks and are hiding in a crouched position, do not use the "throw the bottle into the freezer technique". You will need both of them later. After the soldier leaves the room with the cooks, stay in a crouched position and slowly move along the left side of the table that you were hiding behind. Come up behind the first cook you encounter, in the white shirt. From there, grab him and go into the human shield position with your pistol extended. The other cook may or may not notice that you are there. Shoot the cook that is washing the dishes (or running scared for the alarm). Knock out the cook that you are holding and carry them both into the freezer, as far back as you can go. Turn out the freezer light, then put on your night vision goggles. Turn off the kitchen light and open the door. As quickly as possible, run across the room and hide behind the open door. The guard will enter to turn on the light. As he stops to turn on the light, shoot him in the head. Hide him behind the counter. Next, run out of the open doors and over to the stairwell until you hear the music that indicates that someone saw or heard you. Run back into the room and hide behind the same door as before. The guard will come to turn the light on as before. Do the same thing as you did previously; shoot him in the head. Hide him behind the counter and go back into the kitchen. Get one of the glass bottles by the open window, on the table, and run back through the kitchen, through the adjacent room, and through the open doors. It is now safe to turn off your night vision. Note the guard by the locked door across this huge room. Walk over to the balcony and hum the bottle at him. Sometimes you will knock him out, sometimes you do not. If you do not, you will hear him say either "that's unusual" or "what the Hell...?". Either way, go once more into the room in which you killed the two guards. Hide once more behind the open door by the light switch. It may take him awhile to get up there, but he will also meet the same fate as his two comrades. Shoot him in the head as he turns on the light. That eliminates the guard by the door, thus decreasing the chance of an alarm going off while you take out the second guard in that room. This will be a little trickier. Go out of the room and down the stairs onto the second level. After you get to the bottom of the stairs, go straight into the corner that you are facing. Go to the railing and run back and forth across it until you hear the music that indicates you have been sighted again. Hide back in the corner and wait for him to climb up the stairs. Once he gets up there, you have two choices. Either sneak up behind him and knock him out, or shoot him in the head. Now that you have cleared the room of the two guards, go back up the stairs and into the kitchen. Get the last bottle, exit the kitchen, go back into the room, and down the stairs. Use the computer until you hear Lambert talking. He will tell you that a Colonel is coming and some other things. Hide under the stairs to the left of the computer desk, in the dark by the wall. Wait for the Colonel to get down the stairs and sit in his desk. Throw your bottle at the wall in front and to the left of the Colonel. He will go to see what happened. Sneak up and grab him, thus giving you access to the Retinal Scanner.