not sure which mission that is but what I usually did to collect adam is kill EVERYONE in the area before letting the little sister down....you want to do this bec more splicers, etc. will come running at you...BUT this will lessen the number of enemies you need to kill... once the area is cleared, lay down AS MANY TRAPS AS YOU CAN SPARE... I usually dont use them all but close to it, the traps with the light beam ( dont remember the name ) you can use ALL you have since if they arent triggered you can pick them up afterward.... the motion sensing bombs work well also in open areas and the trip wires work well in doorways!!....and set as many OF THOSE BASTARDS ON FIRE as you can as when they touch each other the fire spreads!!!!....other than that unload all your ammo you can spare and I would suggest upgrading 1 weapon at a time to get the FULL potential, I would suggest the machine gun, it was BY far my favorite weapon in the entire game....hope this helps milk.....happy killing

P.S. SAVE THE GAME EVERY SECOND YOU CAN, most importantly after EVERY SINGLE battle that you get into, or special item you get....I saved damn near a couple hundred times in the whole game lol