You are back in APERTURE LABORATORIES. So, basically, you're back in hell. You had another core with you called Wheatly, a pretty dumb core. Anyways, you see the one and only... GLaDOS again. You go into some weird elevator thing with a lot of buttons. Wheatly tries to find the one to get both of you out but then started an alarm. He tries to turn it off but just messes more stuff up that eventuality wakes GLaDOS back up.

"Oh... It's you."