A decent walkthrough map with a couple of things that bring it down a few pegs, in my opinion.
1. Dr. Walker (whom you have to escort)'s desk is too close to the door behind it, making it time consuming to get him to go around, and the ai nodes leave something to be desired (Dr. Walker won't follow you around corners)
2. When you actually bring him to the elevator, he runs to it, forcing everyone into a cutscene. If you didn't kill all the pit drones by the time he gets to it, you're pretty much guaranteed to fail as he'll get killed by them (ideally, the trigger for him to activate the cutscene shouldn't be enabled until after they're dead)