As you make your way to your house you will encounter a lady with a poodle. After the conversation ends click on the first mailbox(the one on the right). Take the letter you see in the mail box. Go to the back of your house and get the key from under the porch. You have to shake the can. Go to the front of the house and unlock the door with the key. When you enter the house you will see 3 ghosts. Take the letter and give it to the boy on the left. This will open the basement door. Now, go into the door to the right of the girl ghost. Click on the toolbox and then search it, now you have a screwdriver. Go back upstairs and go into the dining room and ignore the lady. Go into the kitchen and click on the sink and open it. Use the screwdriver on one of the screws and go into the hole. Make your way through the tunnels. If you go one way and you can't hear the dripping noise anymore go back and head the other way. Eventually you will find what the noise is. Grab the bag and as soon as you can, go back. Keep going back, don't make any turns and when you get out of the tunnels the achievement will pop.