Hi, is it possible for you to attach screenshot when the freeze happen so we can better understand the problem? You can actually upload screenshot here.
When you enter sewer to find Norman, you actually don't need to click anything. You need to wait for 2 probable situations:
1) The character will give up (she will say she can't take it anymore). Then, you can click exit button to go back to map screen.
2) She finds Norman. There will be small Norman figure show up on the screen in fade-in to signal that you've found him. The game will consider that you've completed the quest. Don't click anything during this time because in less than 2 seconds, Norman dialog will show up. We want to find out which part the freeze happen.
