Sergeant Robert "Bob" Baker was a Vault 51 dweller who perished under ZAX's rule. To teach ZAX about leadership, Vault-Tec arranged for the Sergeant to be assigned to the Vault, with his family placed in a separate Vault as an incentive. The Sergeant would aid ZAX in formulating and carrying out experiments that would help ZAX determine the qualities of an ideal Overseer. The very first experiment was an attempt to implement a democratic, electoral system. Although the Sergeant balked at it being merely the first experiment, he cooperated, convinced that his family was safe.
A month later the experiment proved to be a failure. Although various parties vied for the position, including former State Senator Joel Chambers, supported by his wife, Elizabeth Chambers (at least until ZAX's robotic indiscretion put her on the trail of his indiscretions), nobody was elected leader despite several elections. ZAX determined that voting was pointless and another method would be selected. To this end, it started evaluating the qualities of a leader, using Sergeant Baker (now Sergeant Bob) as a sounding board. Baker inadvertently started the disastrous chain of events that led to the Vault's destruction when he explained that a leader is someone who steps up in a crisis and takes control of a situation, whether they were chosen or not.As ZAX started fiddling with engineered crises in the Vault 51, to force a leader to emerge, Baker observed the deteriorating situation. On July 27, 2078, the Vault almost experienced a mass shooting, until Sgt. Baker intervened, disarming the assailant and killing him with his own weapon, a Colt 6520 autoloading pistol. When Baker confronted ZAX, the machine simply admitted that it was deliberately engineering a crisis to select an Overseer - and if people died, it would simply expedite the selection process. Baker was horrified, but could not stop the machine.
Eventually, ZAX got its way with the death of Helen Marks on August 6. Reuben Gill, driven to madness by her death, went on a rampage that same day. With a gun in hand, he shot every other dweller and started by settling grudges. Clayton Ward was one of the first to go, for taking his room a few months back. Although he could stop him, Sgt. Baker refused to fire when he had Reuben in his sights. 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, not knowing of his family's death. ZAX, in its usual fashion, interpreted his last words to mean that the next cycle should feature better weapons, to accelerate candidate elimination.
Robert Baker is mentioned only in Fallout 76.