Devon began his career as a grunt. Over several years with the Brotherhood of Steel he proved his dedication and combat worthiness. He was given several promotions and received several awards for his accomplishments.
Devon was chosen to participate in a covert stealth team using untested devices. He readily agreed and excelled in the training. Once again he distinguished himself in completing his assignments. Unfortunately, there was no recognition for his efforts because his work was secretive in nature. However, he recognized this fact and accepted it.
Devon was the unfortunate victim of the stealth devices known as Stealth Boys. Prolonged use caused the user to suffer paranoia, delusions, and eventual schizophrenia. When these side effects were discovered, the devices were banned and the team disbanded. However, it was not known that the team had already begun to suffer the effects of the device. Thinking the disbanding of their team to be a conspiracy, they decided to steal the Stealth Boys and form a new covert operation called the Circle of Steel. Devon was left at the base as an undercover operative to cover up the theft of the Stealth Boys.
Since the war broke out between the Brotherhood and the NCR, Ailis McLafferty has been supplying weapons and ammunition to both sides without either knowing and Devon as her secret contact within Maxson bunker. This apparent alliance between the two is merely a ruse for Ailis's own ends, for part of her plan is to eventually assassinate Devon and ensure the downfall of the Brotherhood.
Find the poisoner: Once the commander is cured she will ask to see the Prisoner. She wants to know who poisoned her and why. Upon questioning Devon it will be revealed that he was the poisoner, as well as his association with the Circle of Steel. Depending on how the Prisoner handles the matter Devon may conclude that the Prisoner must be dealt with, but this only leads to his own death.
Successfully Negotiate Peace between NCR and BOS: Apart from simply killing the offending parties, Ailis and Devon can be dealt with through more official routes by exposing their dealings through obtaining their ledgers, thus smoothing the path enough for peace talks to commence.
Find the codes: Devon changed all of the codes for the bunker armory. Without access to weapons and armor, the Brotherhood is rendered helpless against a full on attack.