When you start, switch to Navigation Sense. Go forward, there is a hole in the wall, climb through it. Go straight, climb up the wall here, there's a walkway across the centre, land on it and go through the secret passage. You're now inside the labs. On the opposite wall climb through the vent. Follow it, and the walkway, and the next vent to the end. Follow the walkway and jump down to the right, go through the door and climb back into the next vent. You're now in a bathroom. Drop down, go through the door. Go through the observation room and climb up to the ceiling for the next walkway. Follow the vent, walkway, vent again. Drop down and go through the three doors. There is another vent on the wall, climb up to it and go through it, the walkway, and the next vent. Now go through the next two doors. On your left near the other door is a vent, climb through it. Drop down and go through the door to your left. Follow the doors until you get to the elevator. Climb up the side of the elevator onto the platform. follow the path and turn left. Break the glass and jump through. Now just follow the vent to the end.