The door will jam, shoot a portal through it and escape like that.
The lights will turn off, but Wheatley will turn on a flashlight. Follow him through the dark corridors and past a few jumping sections.
Time for some portals. Jump shoot across where Wheatley illuminates with his torch to keep following him.
Portal your way onto the turret redemption lines and hop across to the next area.
Portal into the turret firing range behind the target wall. When there is a dud turret trying to shoot, put a portal on the target wall and portal over to the balcony behind the turrets.
Walk around the turret lines to the turret control centre. Wait for Wheatley to "Hack" the door, and remove the turret. Go back out to the turret lines and catch a dud turret getting thrown away. Bring it to the control room and put it in the scanner.
Follow Wheatley to the Neurotoxin station and go up top.
Push the red button near the door, and be sure to put a portal at the end of that laser.
Use the moving white walls to cut the pipes going to the Neurotoxin generator with the laser, then follow Wheatley into the tube.
Portal to the white wall in the picture, and get ready for a story segment.
After that nice story segment, put Wheatley in the receptacle and portal to the button that opens up and press it. Get ready for some more story.