Take it Back!

Take it Back! is the twelfth main quest in Fallout 3. It is also an Xbox 360/PC achievement and a PlayStation 3 Trophy. It serves as the final quest in the main game unless Broken Steel has been downloaded.

Attack!
When the Lone Wanderer reaches the Citadel, Owyn Lyons will be briefing his daughter Sarah and Lyons' Pride, in preparation for an assault on the purifier. After informing them of the situation, Sarah's squad is mobilized to wrest control of the purifier from the Enclave. Liberty Prime is activated despite the objections of Scribe Rothchild, who demands it not be used and declares "...it's not ready for field tests, let alone live fire situations - the weapons haven't been calibrated, the navigation detection system is offline..." Despite his warnings, Prime is launched and used without any malfunctions.

To begin the advance on the Jefferson Memorial, one must speak with Sarah Lyons. Note that once the order to attack has been given the green light, all functions, and services in the Citadel will cease. All non-player characters will spout encouraging phrases such as "The purifier is as good as ours!" if spoken to. If the player character has anything to do in the Citadel, they must complete these tasks before commencing the attack.

Following the order to attack, Liberty Prime will be hoisted out of the Citadel on a crane, and the Lyons' Pride will follow it, along with the Lone Wanderer. Prime makes contact with the wall of the bailey on the crane, but it does not damage him. Once outside the Citadel, Prime will begin stomping his way to the fallen bridge, killing everything in its path. Liberty Prime will take down the photonic resonance barriers set up by the Enclave by walking into them.

Once on the bridge, the Enclave will attack Liberty Prime in full force with soldiers, vertibirds, and artillery, but the machine will successfully repel these attacks, aided by the Lone Wanderer and Lyons' Pride. Liberty Prime will subsequently clear the path to the Memorial. The Lone Wanderer and Lyons' Pride can come under attack from targets on a catwalk between buildings after clearing the bridge from the Citadel. Liberty Prime will continue carving his way through the resistance, past the irradiated metro, and onward to a second bridge. At the end is where Liberty Prime stops, and holds his position along with the rest of the Lyons' Pride, while Sarah Lyons and the Lone Wanderer dash inside the Jefferson Memorial through the gift shop. If one hesitates, a significant force of Enclave soldiers will be deployed nearby, either from the bridge or the catwalks around the memorial. Liberty Prime will destroy them. There is light resistance inside the gift shop, usually three or four Enclave soldiers.

The Rotunda
After entering the rotunda, the doors seals shut, with no way to leave. Colonel Autumn is waiting for the Lone Wanderer and Lyons inside, and locks the player character in dialogue. One has two choices at this point: After resolving the situation and heading up the stairs to the control room, a panicked Dr. Li will key the intercom: Project Purity has sustained severe damage in the battle and has become overloaded. It will soon self-destruct if the purifier isn't finally started, but the control room has become irradiated to the point of lethality.
 * Talk Colonel Autumn out of attacking with a series of difficult Speech checks. If Raven Rock was destroyed in the last quest, there will be the option to use an easier Speech check - one can also inform Autumn of Eden's true plans regarding the purifier. However, even with 100 Speech and 5 Charisma, the player character still only has a 50/50 chance of success. After conceding defeat, he will leave the player character to their fate. After this, Sarah Lyons will give a short remark on the player character's decision, depending on one's Karma.
 * Fight Colonel Autumn. The Colonel must be killed alongside his two bodyguards, two standard Enclave soldiers, one of which may be equipped with Tesla armor. It is possible to attack the Colonel and kill him before the dialogue begins, though the soldiers are still hostile.

Final choices
Those with Broken Steel installed have additional options in completing this quest, as detailed in the second decision option. Now, the game has the player character make one final decision: who will activate the purifier. The radiation levels are fatal once the purifier is activated, so whoever goes in isn't coming out (RadAway, Rad-X and Radiation Resistance have no effect on one's survival, as it is a cut-scene).

Decision 1: Sacrifice yourself or Lyons
One choice is that either the Lone Wanderer or Sarah Lyons must sacrifice their lives to get the purifier going and prevent the destruction of Project Purity. If one hasn't figured it out from James' notes and recordings, the purifier password is 2-1-6 (referring to the verse from Revelation which Catherine loved). If the player character follows James to the purifier when he first enters the Memorial in The Waters of Life, James points out the code and repeats the passage. One is supposed to infer it from James' dialogue about the Lone Wanderer's mother, and the picture hiding James' safe in the Vault 101 clinic. If one chooses to convince Sarah to do the job, the Lone Wanderer will tell her the code in dialogue. If one has the Broken Steel add-on, the player character's Karma will be raised by 1000 if they decide to activate the purifier themselves. Karma is unaffected if Sentinel Lyons or one of the player character's companions is sent in.

Without Broken Steel, if the player character chooses to sacrifice themselves, once entering the password they slump away from the purifier password panel. A statue of Thomas Jefferson is revealed inside the central chamber as it is purged. A series of still images recounting the player character's actions throughout the game is shown. The relevant section of ending video ends with Sentinel Lyons looking at a shining pile of goo at the control chamber's bottom - which is, presumably, all that is left of the Lone Wanderer.

Contaminating the water (Optional)
If one chooses to activate the purifier themselves, this is the time to insert the modified FEV created by President Eden into the water filter, assuming one wishes to and did not give it to Elder Lyons. As in Fallout 2, the only creatures spared by the modified FEV are pure strain humans who are still within vaults and the Enclave. This would reverse a great deal of genetic damage done by the nuclear apocalypse but at the cost of complete eradication of nearly all life on the wasteland. This decision is actually listed in the player character's Pip-Boy 3000 as a separate quest called Project Impurity; however, it cannot be completed if one turned in the modified FEV to Owyn Lyons before departing the Citadel.

Inserting the modified FEV lowers Karma by 1000 and has a long-term game impact if one has Broken Steel installed. The Aqua Pura thus created by purifying the water is now infected by the virus and as the player character is not a pure-strain human as Eden believed, it will cause a negative effect on their SPECIAL stats and kill the Lone Wanderer if four or more are consumed in quick succession. A warning will come up that reads "Continued consumption of FEV-laced water will be fatal" to remind one of this fact.

Decision 2: Have your radiation-resistant companion do it
Without Broken Steel installed, the Lone Wanderer's companions will refuse to do the job. Naturally, of the seven, four would die just as easily as the Lone Wanderer and they are not willing to do it. Even Fawkes, Sergeant RL-3, and Charon who are highly resistant or immune to radiation will simply decline. With Broken Steel, however, the latter three will now agree to do the job, as they can do it safely.

Companion Responses
Fawkes, one of the companions the player character may take with them, has great radiation resistance (or possibly immunity) as a result of being a super mutant. However, like any other companion character, his dialogue option has him refuse to enter the chamber, mysteriously claiming it is the player character's "destiny." Fawkes may nonetheless follow the player character into the chamber if his following distance is set to "close."
 * Fawkes

If the Broken Steel add-on is installed before beginning Take it Back!, Fawkes will agree to enter the chamber, stating this.

Fawkes will be briefly staggered when the purifier activates but does not collapse as the player or Sarah Lyons would. He will instead walk around the chamber and kick the purifier panel as the screen fades to white. The end will show him as "A True Hero" instead of Lyons.

There is no option to have Dogmeat activate Project Purity. Instead, a new dialogue option opens up, wherein the Lone Wanderer can say some final words to his or her canine companion, stating: "I think it's time for us to say goodbye, old buddy. Take care of yourself, okay?" Dogmeat whines in response.
 * Dogmeat

Even if one took Sergeant RL-3 (a Mister Gutsy combat robot, which is immune to radiation) into the rotunda and command it to go in to turn on the purifier he declines and says:
 * Sergeant RL-3

There is no Robotics Expert dialogue option in the conversation.

Like Fawkes and Charon, if Broken Steel is installed before starting Take it Back!, RL-3 can be ordered to go into the control chamber and activate the purifier. He will state that his "superior design and programming" will be able to withstand the hostile environment, followed by an exclamation that "this will mean a battlefield commendation for sure."

After starting the purifier, he cringes but is otherwise unharmed. The ending will show him as "A True Hero" instead of Lyons.

Charon will not activate the purifier. The dialogue is as follows:
 * Charon

Just like Fawkes, if Broken Steel has been installed before this quest, Charon can be told to enter the control chamber and turn it on. The player character will remind Charon that he must obey whoever holds his contract, then order him to enter the control chamber, to which Charon grudgingly agrees.

Unlike with Fawkes or RL-3, no mention is made of the fact that Charon, being a ghoul, should be unaffected by the radiation in the chamber. If Charon is used to start the purifier, he will replace Sarah Lyons as "A True Hero" in the ending movie.

Butch will refuse out of fear of dying and of becoming a ghoul, stating:
 * Butch

Star Paladin Cross refuses, stating:
 * Star Paladin Cross

Clover refuses as well:
 * Clover

Jericho also refuses, stating simply:
 * Jericho

Decision 3: Do nothing.
If one chooses to, they may simply not go into the purifier. This results in Project Purity quickly exploding, along with any chance of pure water for the entire wasteland or to introduce the modified FEV into the water supply. An ending sequence will still be played, and it will count as an ending (completing the quest and unlocking the "Take it Back!" achievement/trophy). The last thing the player character will see is the destruction of the purifier. Just like all other endings, this does not result in free-play. Even if Broken Steel is installed, this option ends the game. With no purifier the events of Broken Steel could not happen.

Conclusion
In all events, completing this quest will present one of the Fallout 3 endings. However, depending on one's choices and the game's installation, the game could either continue into the events of Broken Steel, or simply end.

Game over
The credits will roll and return to the title screen, if:
 * The Broken Steel add-on is not installed, there's no continuation after this mission regardless of the decision made (sending Sarah or not, or even letting the purifier explode).
 * The Broken Steel add-on is installed, however:
 * The purifier is destroyed (by not entering the correct code or allowing Sarah to do so), or
 * A companion manages to enter the chamber along with the player character (running around to the furthest side from where you entered, having your companion glitch into the chamber).

Broken Steel
However, if Broken Steel has been installed and the player character activates the purifier instead of allowing it to explode, the player character will wake up two weeks later at the Citadel.

As the Lone Wanderer wakes up, they encounter Elder Lyons, who explains that both they and Sarah Lyons were both knocked unconscious due to an energy spike in the purifier and were found and brought back to the Citadel. Sarah has either died, if she activated the purifier, or has not yet recovered from her coma if she didn't. Elder Lyons also explains the consequences of their actions, including the destruction of Raven Rock or the insertion of the modified FEV into the purifier. The first Broken Steel quest, Death From Above, starts here.

Ending
The ending varies depending on how the player plays the game, and some of the largest differences are seen depending on what the player has done during Take it Back! See Fallout 3 endings for more info.