You'll get this during the time at the store. You will have to go and rescue Glenn at a small apartment area and then save a woman trapped in an upstairs apartment.
When you first hear the woman, you all hide behind the wall. Lean out to the left and pick up the pillow. Then move all the way to the right to the truck and look in the window. You will see an ice pick which you can't get to because smashing the window will cause too much noise. Move to the left side of the truck and you will see a walker sat against car. Use the pillow on it and Carley will shoot him, using the pillow to muffle the sound.
Open the door to the car and take the spark plug. Then use the lever to move the car. It will trap another walker against a wall. Go back to the truck and use the spark plug on the window. You can now get the ice pick.
Go back to where you got the pillow and sneak over to the van in the middle. To the left of the van, you will see a walker. You can lure it over and quickly kill it with the ice pick. The kill the one trapped against the wall by the car and take the axe behind it.
Go upstairs and kill the two walkers with the axe. Use the axe on the door and talk to the women, who will come out.
*** Spoiler - click to reveal ***You'll find she has been bitten. Either give her the gun to shoot herself or walk away. Which ever choice you make, you'll get the achievement.