Portal 2 Walkthrough - Chapter 4: The Surprise

This Portal 2 Walkthrough will cover Chapter 4: The Surprise. It seems that GLaDOS has a surprise waiting for us, a real one, and that probably isn't a good thing. Thankfully Wheatley has an escape plan. If you need help getting through tests 17-21, and then successfully escaping with Wheatley past the turret ambush, just look here at this section of the guide.