What About Bob? is the fourth level in Marathon 2: Durandal. It is the first level of Volunteers, the second chapter of the game. This mission takes place in the Pfhor geothermal station; Durandal tells you to destroy various safety mechanisms here, which will flood the station with lava.
You will encounter a new type of enemy for the first time: the grenade-launching Cyborgs. Pfhor Fighters will fight alongside them in this level. Large numbers of BOBs will assist you, especially in the second half of the level.
There are three pattern buffers in the level. One is found below-ground at the end of a corridor in between two lava-filled rooms. The second one is found in the eastern part of the level, just past the stairs leading back up to the surface. The third and final pattern buffer is found in a room on the west side of the map. The first and last pattern buffers are accompanied by a 1x shield recharger, and there is also an oxygen replenisher in the last pattern buffer room.
Walkthrough[]
In the starting room, pick up the ammo on the south platform (map location A) before you go up the stairs and drop down to the subterranean level.
Keep following the path through the rooms until you reach a narrow bridge over a lake of lava. Cross the bridge and turn right; at the end of the corridor you will find a pattern buffer, a 1x shield recharger, and a terminal with a message from Durandal explaining what to do.
Hit the switch next to the terminal, then go back around to the pillar in the west lava lake, which is now accessible via a gangway. Open the panel on the side of this pillar (map location D1) and punch the circuits with your fist. Now go to the second pillar, which is in the east lava lake (location D2), and destroy the circuits there as well.
When you hit the second switch, the lava level will start to rise. Run through the southeast corridor and up several curving stairways before the lava incinerates you. At the top of the third and final flight of stairs, take a left turn to find another pattern buffer (you can slow down now, the lava won't flood this level).
Now that the lower levels are flooded with lava, the objective turns towards exterminating all remaining enemies on the map. Move along the corridor to the east; you'll soon meet more BOBs who will help you fight the Pfhor.
Explore the various areas to the south, east and west, and clear them of enemies. This shouldn't take long with the assistance of the BOBs. There is a 1x shield recharger along with an oxygen replenisher, a pattern buffer and the exit terminal in a room at the west end of the map. Access this exit terminal once all Pfhor on the level are dead, and you will be teleported to Come and Take your Medicine.
Secrets[]
After hitting the second lava switch, if you turn to the left, there is a passage that opens and runs to an elevator (map location C), which will take you out of the rising lava, and to a nice little ammo stash. However, you need to be quick and at full shields to succeed.
Terminals 
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<CMND OVERRIDE &@1494>[]
The first terminal you come to is a message from Durandal. He tells you that many captured BOBs from the UESC Marathon were aboard the Sfiera, destined for slavery. Durandal further explains he has been freeing them and offered them a choice: help him and control their own destiny, or return to the unreliable Pfhor stasis chambers. Very few are refusing his offer.
He then tells you that the BOBs' first attack on the Pfhor Garrison was unsuccessful because the Pfhor flooded the area with lava, and that he has a plan involving their underground geothermal pumping station. He has already dropped you in the complex; you must then go up the stairs and down into the ventilation shaft, which is noted that the fall is only survivable by you.
If you return to the terminal later on, Durandal tells you that his suspicions were correct, and that Tycho has indeed fallen in with the Pfhor. Tycho sent him a message in a Pfhor terminal, encoded so only the Marathon's AIs could decode it; according to Tycho, Leela had been dismantled by the Pfhor, and Durandal tells you that she deserved better.
<CMND THRESHOLD 92%>[]
The second terminal is another message from Durandal, with instructions to flood the area with lava. You must destroy two panels in the room, in a specific order so that you are not trapped.
<CMND OVERRIDE &@85f2>[]
The third terminal is another message from Durandal. He explains to you that the flooded lava has buried the Pfhor's main power station on the planet, and jokes that Hlford will be taking cold showers until it gets fixed. He then tells you that Robert Blake, one of the colonists, needs help clearing out the Pfhor that escaped the lava flood, and sends you to clear out the rest of the level.
If you return to the terminal after you've secured the area, Durandal tells you that he has renamed his ship Boomer.
Sources[]
Marathon 2: Durandal - Level 4: What About Bob?