| ||For the Gunners sergeant found in the Quincy ruins, see Baker.|
Formerly a sergeant with the United States Armed Forces, Robert Baker was assigned to Vault 51 to advise the vault's ZAX artificial intelligence in finding the best way to select an overseer. Baker was concerned with the safety of his own family, and agreed to help ZAX learn about leadership knowing that his wife and children were safe. Baker first proposed a democratic vote to select the overseer, but it ended in failure when candidates voted for themselves, factions were formed and no one gained a majority. ZAX was not satisfied with the results, even after different types of elections were tried, and attempted to cut off any more votes. Baker stopped him, and mentioned that in his eyes, a leader was someone that stepped up in times of crisis. Unknown to Baker, this description of a leader doomed the vault to its deadly fate, as ZAX tried to create these crises from that point on.
ZAX began to psychologically manipulate Vault 51's residents and create conflict, even going as far as to plant weapons in the vault. When a resident with a gun nearly committed a mass shooting in the cafeteria on July 27, 2078, Baker disarmed the perpetrator and killed him with his own weapon. Baker confronted ZAX with the firearm, to which ZAX flatly admitted that it was creating the crises to speed up the overseer selection process. Unable to believe what he was hearing, Baker stormed out of the room and refused to help ZAX anymore.
After Reuben Gill went on a rampage, killing many of the vault's remaining residents on August 6, 2078, Baker had Gill in his sights but could not bring himself to kill anyone else, fearing that Gill's death would perpetuate a cycle of murder. He retreated to his room and barricaded himself in. ZAX was puzzled by Baker's behavior and refusal to receive medical help, but it did entertain his last request and revealed that Baker's family was killed in the nuclear fire that engulfed Appalachia. With nothing left to live for, Baker died in his quarters, finally knowing of his family's death. ZAX interpreted part of his last words to mean that the next cycle should feature better weapons, to accelerate candidate elimination.
Sergeant Baker is also referred to as "Garrison Baker" in the updated credits, as well as Baker's editor ID.