The Spencer Mansion was the brainchild of prominent New York architect George Trevor. After Ozwell E. Spencer outlined his wishes for his own private getaway on the outskirts of Raccoon City, Trevor visited his office one day in 1962 with a host of design plans which were immediately approved. Work began later that year and Trevor estimated the project would take five years to complete. Unusually for a private residence, Spencer requested that the mansion be fitted with a host of secret rooms and hallways, each interlinked by a series of clever puzzle locks. Trevor didn't question it at the time and considered it as part of the challenge, which if completed, would be recognised as the finest work of his career.

The mansion itself was completed in the summer of 1967, with Spencer himself moving in in July. The laboratory facilities were not completed until November later that year. The mansion itself was simply to act as a front for the research areas housed beneath that would go on to see decades of illegal bio-weapons research being carried out.
To ensure the mansion lab facility remained a secret, Ozwell E. Spencer had George Trevor and his family killed. But rather than simply eliminating them, he used them as test subjects for the Progenitor Virus, which Spencer and his colleagues had discovered a year previous in Africa. After experiments on both Trevor's wife Jessica, and his daughter Lisa, George Trevor himself was allowed to escape. For the better part of a week, he wandered the many underground tunnels in a bid to escape, yet all along this was simply a ploy by Spencer to test out the efficiency of the mansion's security and Trevor was led to his own purpose-built gravestone where he perished, lost in the depths of his own creation.

The mansion itself was located in Raccoon Forest, some miles from Raccoon City and roughly a mile away from the Executive Training Facility run by Dr. Marcus. The main building consists of two floors serving as a residence for Umbrella VIPs and senior research living areas. Each room is lavishly furnished, filled with expensive art pieces and sculptures. Highlights include an expansive dining room, library and a grand hall. There is also a large attic space for storage. The estate also includes many acres of garden landscape, expanding into the forest and a Guardhouse for staff and other employees which also includes a rec room and entertainment facilities. Beneath the Guardhouse is a giant Aqua Ring home to the ferocious Neptune sharks.

There is also a heliport and access to the main lab comes via a hidden elevator concealed beneath a water feature in the main courtyard. It is down here that many of Umbrella's henious crimes were born. Albert Wesker and William Birkin were stationed here as Chief Researchers during the seventies and eighties and it was also here that the G-Virus was born and the ultimate biological weapon, Tyrant was created.
The lab consists of four floors - the first of which being passage to the heliport. The B2 level houses the Visual Data Room where archived data is stored. B3 contains a computer room, some experimental rooms and a mortuary. It also contains the 'power-maze' which supplies electrical power to the whole estate. Finally an elevator to B4 leads to the main laboratory and the Tyrant Incubation chamber. A small prison is also located on this floor.

The mansion kept its cover for over 30 years until may 1998 when the T-Virus was leaked throughout the facility. The initial reports suggested the leak was due to an accident by the careless researchers there, but it was later confimed that the virus was scattered intentionally by the mutated Queen Leech having adopted the personality of the deceased Dr.Marcus.

The mansion was put into lock-down and one by one, all the employees stationed there fell victim to the virus. When the B.O.W. test subjects escaped their confinements, the facility was deemed a total loss.

Cerberus dogs now roamed Raccoon Forest, feasting on hapless hikers and joggers and eventually the Special Tactics and Rescue Service were called in to investigate the situation. The operation was used to Umbrella's advantage for it presented an excellent opportunity to collect raw combat data on the various B.O.W.s running loose. What they didn't plan for however, was the S.T.A.R.S. members being able to escape the facility and Umbrella's own secret operative, Albert Wesker, apprantly being killed, resulting in no combat data being delivered to Umbrella.

The Spencer Mansion and Arklay Laboratories were destroyed on the morning of July 25th 1998 after the self-destruct mechanism was activated. All research data and B.O.W. test subjects were wiped out.