Underground Bunker is the 17th mission in Syphon Filter 3. It is the third and final level where Teresa Lipan is the playable character. It picks up where the last mission left off and continues to depict Teresa's past as an ATF agent. With the satellite data now in her possession, all that is left for Teresa to do is rescuing the Oaktons and getting them out of the area safely.
Oakton Compound, Western Montana:
Teresa's Testimony from the Congressional Record
"Getting Oakton's family to trust me was tough, but I knew that the only way to get them off that mountain safely was through their underground bunker system. A lot of those survivalist compounds had been built right over the top of old mines, giving them access to a network of hidden tunnels."
"I had always thought the Oaktons were more paranoid than most because they had created an entire compound down there. Looking back, I guess it wasn't so paranoid. It was hidden pretty well, but the NSA hitsquads were coming fast, and I not only didn't know the way, but had a pregnant woman in tow, and she wasn't moving all that fast."
When Teresa Lipan reaches the bunker, she is met by a suspicious Dusty Oakton who demands to know who she is and his father’s whereabouts. Teresa replies that his father sent her to rescue him and his mother, Debbie Oakton, in order to gain his trust. Dusty then mentions that his mother is in labor to which Teresa requests to take her where she is and assures him that she will get them out of there. Dusty then leads the way towards Debbie’s location with Teresa protecting him along the way from the NSA agents, who have managed to break into the bunker. Dusty also sets up explosives to slow the NSA agents down. He also trusts Teresa enough to allow her to get some supplies and weapons in the bunker. He also gives her infrared goggles to go through the darker paths of the bunker.
When they reach their destination, Debbie asks his son who Teresa is and where his father is. Dusty replies that Teresa is there to rescue them and that she can trust her, even going as far as calling her a friend. Teresa informs Debbie that they need to get out of there immediately because the NSA have managed to break into the bunkers and the security doors won’t hold them out for much longer. Because Debbie is in preterm labor (barely 30 weeks) and thus immobile, she asks Teresa to go into the food cooler room to get the first aid kit containing terbutaline so that she can administer it to Debbie, which will delay her labor and allow her to move. While Teresa goes to find the first aid kit, Dusty stays with Debbie to watch over her.
After finding the first aid kit and going back into Debbie’s room, Teresa manages to kill a few NSA agents who are attempting to kill all three of them. Dusty also manages to arm himself with an M-16, which he obtained from a supply closet. Teresa then gives the terbutaline shot to Debbie, allowing her to move albeit at a very slow pace. Teresa then escorts Debbie while protecting her from the NSA agents. Meanwhile, Dusty goes to the computers to back up data files. After backing up the files, Dusty destroys the computers and proceeds to help Teresa escort Debbie to the main room. When they reach the room, Dusty sets off some explosives in the entrance to slow the NSA agents down “for good”. Dusty then opens the secret passage (behind a US flag) so that they can go in and escape the bunker through the ladder. Before joining them, Teresa kills a few more NSA agents who have managed to get in the room through openings in the ceiling. Teresa then contacts Gabriel Logan to pick them up.
In the closing cutscene, Teresa tells Vince Hadden in the testimony that Gabe lifted her and the Oaktons out of there with a chopper. Hadden then asks her what she has been doing ever since faking her death at the hands of Jason Chance. She replies that she has been mostly pursuing Mara Aramov. She then tells Hadden that since Aramov thought that she was dead, she wasn’t watching for her to cover her tracks as she usually does. Meanwhile, Mara Aramov sneaks up in the hearing room. Teresa then states that the most interesting place she found Aramov was in Hadden’s office where they were talking with one another, exposing Hadden’s connections to Aramov and his involvement with the Syphon Filter conspiracy through the Agency and the Consortium. Officers then show up with Gabriel Logan to arrest Hadden but Aramov shoots everyone in the room, killing Hadden and wounding the officers. Aramov then exits the room, with Gabe following suit. Teresa stays behind to tend to the wounded officers.
Follow Dusty down the tunnel, when he stops to plant something immediately go past him because he is setting explosives which will go off when he's done. After that, follow him down until he stops so you can get some supplies, there is a Falcon on the green-lit cave on your left. Go back to where Dusty is and go down the cave to the right, there are four NSA agents here so take them all out. Follow Dusty down until he stops in an extremely dark cave, take out the two NSA agents that appear and he'll give you some night-vision googles to help you see. Take the M-79 in the box on your left and follow Dusty down some more tunnels until you get to a spiral ramp-like structure, shoot the two NSA agents in here and continue on. You'll get to an underground room with two more agents, kill them both and pick up the Flak Jacket in the box on the right. Afterwards, follow Dusty to the room where Debbie is.
Exit the room where the Oaktons are, facing away from the tunnel that leads to the room turn left and enter the first left corridor, you should be in a room with computers. Exit it through the tunnel on the right, turn right and head down the very last tunnel on the right, (it should lead down). You'll see two grey doors, press Action to kick them open and the First-Aid kit is on the left. Return to the Oaktons taking out all NSA agents you run into.
Protect Debbie, ignore Dusty since it's Debbie you want to protect. Follow her as she walks and take out any NSA agent daring enough to attack, soon she will enter an elevator and all three of you will ride down a level. Follow Dusty, since he will attack with you, to clear the path ahead of any NSA agents and eventually you'll get to a conference room. Dusty will set-up some charges and two more agents will run through the doorway, kill them both and Dusty will set off the charges, escape through the secret path he opens to finish the mission.