Dead End Job

I would do this on the Buisness District, 1st area where you start being able to select missions, on a low level map, 1 ghost highlighted for difficulty. Once you start just go to the 1st room blasting ghosts and then vacuuming them up. Once you have cleared all ghosts you will get a notification that that room was cleared. You will have to do this with every room, usually about 8 to 10 rooms in the level. In the process of this you will save the trapped citizens in the level that will allow you to finish the level. Head towards the elevator once you all done and enter it to finish the level.

The mini map in the top right corner of the screen shows all rooms you have entered as turning white from black. It turning white doesn’t mean you’ve cleared it, only that you entered it. The elevator room has a little black arrow sign on it to show you it’s location.

You may have to fight a small mini-boss in the elevator room when going for the exit. They don’t always appear. You deal with these same as the lesser enemies, they just take longer to kill.

It seems the 1st tutorial mission doesn’t count for this Achievement.

Good luck with the Achievement.