Parts of Jaime's personal journal can be found as audiologs spread throughout the building. The transcripts reveal that he was a traveler who set out searching for his father after he left him alone in a hospital and "went crazy" after acquiring a mysterious book (the Krivbeknih). Jaime tracked his father south from an unknown location across vast distances.
He eventually fell in with another group of travelers who, as it turns out, were violent raiders. It was not long until they killed a family for a "sack of rotten vegetables." Jaime secretly resolved to get away from this dangerous group as soon as possible.
The opportunity to escape presented itself when the raiders prepared to attack a group of traders. Jaime turned on the raiders, earning the thanks of the traders. Grateful, the trader group told him where his father headed. Following his father's trail Jaime headed to the Dunwich Building. He eventually found his father who had, by that time, become a ghoul. In his audiologs, he recalls hearing the raiders tell "spook stories" about "zombies" inside, which were apparently true. Afterward, Jaime picked up a strange book his father had been keeping and decided to rest against an unusual obelisk in the bottom of the building. Upon awakening, he had begun the process of mutating into a ghoul due to the radiation emitted from the obelisk (you can hear Jaime mutating at the end of Jaime's personal journal entry 08 and throughout entry 09).
The plot line is a reference to the Cthulhu mythos of writer H.P. Lovecraft, and especially his short story, The Dunwich Horror. (According to a terminal in the building, the company owning the building was named "Dunwich Borers.")