Seventeen years after the events of the original Marathon, the AI Durandal awakens you from stasis and sends you down to the planet Lh'owon, the homeworld of the S'pht. Your objective is to install two Uplink Chips in a Pfhor water treatment facility so Durandal can access the Pfhor planetary computer network.
There are two pattern buffers in the level, in the southeast and northeast corners. A 1x shield recharger is located in the southeast pattern buffer room. There is also an oxygen replenisher in a secret room on the west side of the level.
At the start of the level, you'll be assisted by five BOBs. Unlike the BOBs from Marathon 1, these ones are actually useful in a fight, as they are armed with Magnums. After clearing out the first area, they'll teleport out, leaving you to proceed further through the level by yourself.
Just to the northwest of the starting position, you'll find the game's first terminal. Durandal will explain your objective: find two places on the map where uplink chips need to be installed. He'll teleport the chips in when you're there.
Make your way to the southeast corner of the level. You'll find the first place to install an uplink chip there; you can hear the uplink panels because of the electrical humming they make. A chip will teleport in when you approach the panel; walk over it and press the action key when facing the panel to install the chip.
Proceed through the area until you find two panels that are missing chips; you can hear them because of the electrical humming they make. When you approach them, the Uplink chips will teleport in. Walk over them to pick them up, and press the action key to install them on the panels.
In the southeast room where you install a chip, you'll also find another computer terminal with some backstory, a pattern buffer where you can save your game progress, and a 1x shield recharger for restoring your health. You can return to the pattern buffer and shield recharger whenever you need to later on.
Now go to the northeast part of the level. Some more BOBs will briefly assist you along the way. You can install the second chip in the northeasternmost room; there's also another another pattern buffer there. In another room further to the west you can pick up an MA-75B Assault Rifle/Grenade Launcher.
Once both chips are installed, return to the first terminal. There, Durandal explains that it has been seventeen years since the attack on the UESC Marathon, and that he has since been searching for Lh'owon -- the S'pht's home planet -- trying to find a weapon to use against the Pfhor. You are then teleported to The Slings & Arrows of Outrageous Fortune.
Next to the first terminal, there's a light switch overlooking the western room with a water pool. On the back of the switch panel, there is another switch (see location A on the map); hit this switch, then drop down into the pool room.
On the center of the west wall, there is a secret door (from a distance it appears darker than the surrounding walls) that will open to reveal a short corridor.
In the room beyond you'll find a large pool. There's a switch across from you that lowers (or raises) the water level in the room. At the bottom of the pool, in the southeast corner of the room, you'll find an oxygen replenisher and a switch that activates a nearby elevator taking you back out of the room.
Back in the western water pool room (marked A on the map), you can grenade jump onto the ledge in the northwest corner of the room. Drop down into the water tank; an elevator platform will rise out of the water. At the north end you'll find a hidden tunnel (map location C) leading to an ammo cache in the dark room to the north.
In that same dark room (marked D on the map), there is a hidden door in the wall in the southwest corner. It'll lead to an elevator; at the top of the elevator, there are a couple of passageways overlooking a large lake. Go west, then south to find a WSTE-M5 Combat Shotgun along with some ammo.
The first terminal you come to is a message from Durandal, explaining that you have just come out of stasis, but he refuses to tell you why you were in stasis and why you're missing your weapons. He orders you to install two Uplink Chips in Pfhor terminals so he can access their data network, while he carries out an orbital bombardment to keep the Pfhor occupied.
The second message, found at the end of the level, explains that seventeen years have passed since the events of Marathon 1. Durandal reveals that he, along with the S'pht who were freed from slavery at the end of the previous game, have spent the intervening years travelling all around the galactic core in their captured Pfhor ship. They were looking for Lh'owon, the S'pht homeworld that was ruined over a thousand years ago in the war in which the Pfhor enslaved the S'pht. They finally found Lh'owon sixteen hours ago, and are looking for weapons or knowledge to use against the Pfhor.
The second terminal is a Pfhor computer. It contains a message from Pfhor Garrison Command, stating that Durandal's orbital bombardments have caused major damage to the water purification systems. The local station commander is ordered to deploy three drones to make emergency repairs.
- The Windows 95  version of the level contains a number of level design differences. The most notable change is a hidden recreation of the entire first level of Marathon 1, accessible through a secret underwater passageway in the north uplink room. This is not included in the Aleph One version of Marathon 2, which is based on the Mac version.
Marathon 2: Durandal - Level 1: Waterloo Waterpark