To unlock this achievement you will need to find and kill the ghost during the mission 'Traditions of the Trade'. You will find the ghost in the long corridor that leads to the crime scene room. You will know which corridor it is as there are 4 open windows with their curtains blowing around eerily. You will need to get to the corridor quickly in order to see the ghost. If you happen to miss it, or it doesn't show at all, you can simply run back out of the closed wing, then turn around and run back to the corridor to try again. The only way to kill the ghost is with the fiber wire. You need to be behind it as it turns, in the corridor and quickly press to kill it with the fiber wire.