Some time after the Chosen One stopped the Enclave on the West Coast, the Brotherhood of Steel ruling council decided to send a contingent of soldiers to the East Coast with a mandate to recover all advanced technology from the Washington D.C. area and to investigate the reports of super mutant activity in the area.
And so, when she was seven (and her mother having died several years earlier), a small but hardened contingent of Brotherhood of Steel soldiers, led by Sarah's father, an idealistic paladin named Owyn Lyons (accompanied by his friend and technological adviser ScribeReginald Rothchild) set out from the Lost Hills Bunker in California. This started the long trek east to what was once Washington D.C.
A permanent base known as the Citadel was built into and beneath the ruins of the Pentagon. Owyn Lyons (now Elder of the Capital Wasteland division of the Brotherhood) and his soldiers also found the super mutants in the urban ruins of downtown D.C. and helped to stop the mutant tide from overtaking the entire region.
In 2277, Elder Lyons' daughter Sarah is now a grown woman, but she is still one of the Brotherhood’s finest warriors, if not the fiercest. In fact, she’s the only member to have achieved the illustrious rank of Sentinel, and now commands her own elite squad, Lyons' Pride.
Sarah is unsurprisingly loyal to her father, but her superior attitude to wastelanders is more typical of those in the Brotherhood with lingering sympathies for the Outcasts. She has little patience with 'civilians' stumbling into the line of fire. However this may be the pride of a professional rather than someone who doubts the value of the Brotherhood's objectives. Her attitude to Initiate Reddin suggests she is not convinced that wastelanders should be recruited into Brotherhood ranks.
Take it Back!: Sarah, after inducting the Wanderer into the Pride, briefs you all on the mission to come. She personally accompanies the Wanderer into the Jefferson Memorial Rotunda for the final confrontation with the Enclave's second in command Colonel Autumn and his handful of personal guards. Based on the Wanderer's choice, Sarah Lyons will:
Watch the Wanderer's selfless act of sacrifice in choosing to enter the chamber and mourn his/her inevitable demise (unless Broken Steel is installed).
Enter the chamber herself, sacrificing herself in place of the Wanderer.
Wait until the Purifier explodes.
Who Dares WinsBroken Steel: After the player escapes from the mobile base, Sarah Lyons will appear again (unless she was killed) and pick the Lone Wanderer up in a vertibird, taking you back to the Citadel.
She will comment if the player is wearing power armor when fighting the Behemoth in the GNR plaza, saying he/she can wear it for helping them defeat it.
Broken Steel If the player activates the purifier himself/herself, or uses Fawkes, Sergeant RL-3 or Charon to start it; it is revealed that an energy spike knocked her and the Lone Wanderer out. Two weeks later after the Lone Wanderer wakes up, she's still in a coma, "unresponsive but stable".
Broken Steel If Lyons activates the purifier, she will be killed by the radiation and doesn't appear again.
Broken Steel After completing all the main quests, if you choose to destroy the Enclave, she will comment that she wishes she could get to know the Lone Wanderer better, hinting possible romantic feelings for him.
Broken Steel If you betray the Brotherhood instead and launch an orbital strike on the Citadel, she and the other Brotherhood members who picked you up will attack you in a fury, calling you a traitor. It is then possible to kill her, as she will no longer be an essential non-player character.
Although her stats are normally on par with a normal Brotherhood of Steel Paladin, during the final quest "Take it Back!" her health is increased to 505, giving her extremely high durability on par with Star Paladin Cross while she fights alongside the player during the game's final battle. Additionally, as a plot-critical non-player character, she cannot be killed by the player or other characters during the course of the game, merely knocked unconscious.
Sarah Lyons is coded as an non-player character companion, and therefore uses up ammunition for her weapons, unlike most standard non-player characters. She has more than 100 microfusion cells in her inventory to prevent her from running out of ammunition under normal circumstances.
After you destroy the Enclave at the end of Broken Steel, the first thing she will say to you afterwards is, "When I first saw you long ago in that alley Chevy Chase, I thought you were just some trashy Wastelander. I'm glad to see I was wrong.", even if the Lone Wanderer never completed the Galaxy News Radio quest.
xbox360ps3pc At the end of the game Sarah Lyons can glitch into either saying that the control room still isn't clear or repeat the phrase "Steel be with you!" [verified]
xbox360 After Waters of Life, before speaking to Rothchild to start the quest Finding the Garden of Eden, Lyons will appear on the road leading from Arlington Library to the Flooded Metro, walking along the road to a point past the Nuka-Cola Plant. [verified]