(Covers information from Anderson's universe)
Dr. J. Isaacs was a senior virologist and geneticist within the Umbrella Corporation. He played a major role in Umbrella's T-virus research during the global T-virus pandemic, but was ultimately killed after mutating from viral infection and going rogue.
Isaacs was born around 2002 as part of a top-secret doomsday project, wherein a number of VIPs from within and outside of the corporation were to be placed in suspended animation in Raccoon City's Hive complex and have their clones assume their respective roles and inevitably die in a planned pandemic. In Isaacs' case, he was a clone of Umbrella's chairman, Dr. Alexander Roland Isaacs. He was not allowed to know this information, however, and was given implanted memories to fit the role of a senior researcher, with the real Isaacs' aide Albert Wesker assuming the position of Chairman.
When The Hive fell to a T-virus outbreak, Isaacs recovered infected survivors Alice and Matt Addison and began research on them at Umbrella's medical facility within Raccoon City Hospital, where they were exposed to large viral loads of T-virus to stimulate mutation. In Alice's case, she developed superhuman abilities as part of "Project: Alice" or "Program: Alice", while Addison mutated extensively and was given cybernetic enhancements to allow for remote control, codenamed "Program: Nemesis". Isaacs left the city the same day, either before or during Umbrella's emergency evacuation of personnel when Undead escaped out into the city.
Following the destruction of Raccoon City with a tactical nuclear missile, Umbrella's security force traced a wayward UBCS helicopter to a crash site in the Arklay Mountains. Isaacs landed in one helicopter to recover the body of Alice, who had been severely wounded in the crash and had sustained burns to her face. Over the next three weeks he oversaw her body's regeneration from the Umbrella Medical Research Facility in Detroit, and it was either here or back in Raccoon City she received cybernetic enhancement which allowed the company to see through her eyes. When Alice finally woke up, she fought her way out of the lab and into a car driven by fellow Raccoon City survivors who had come to rescue her. Under Isaacs' instruction, they were allowed to drive away while Alice's cybernetic enhancements kept him informed as to her whereabouts.
In spite of efforts to sterilise Raccoon City, the pandemic began as planned with an outbreak in Tokyo, though it is possible the virus also bypassed Raccoon City's blockade. With the virus spreading through international travel routes, national governments soon collapsed, unable to protect themselves. Over the next five years, Isaacs became Umbrella's senior-most remaining researcher and placed in charge of their Science Division. He would remain within the walls of an underground facility in the Mojave Desert under the control of Slater. Being the last remaining North American outpost, Slater and Isaacs served in international committee meetings as representatives of North America in general, with Slater representing administrative matters and Isaacs, scientific.
During a meeting around 2007, Isaacs presented his findings on the Undead, where he determined they did not require sustenance and so could survive for decades even without food. Rather than find ways to eradicate the Undead, Isaacs' research steered instead towards easing the symptoms of the T-virus disease so the Undead could regain some degree of cognitive ability and serve the human survivors as a docile workforce. For this, however, he required a blood sample from Alice so her antibodies could be used. Having gone off the grid some years prior, this was not a simple solution. To get around this, Isaacs had for several months worked on producing clones which could be used for study, but these clones were considered genetically-defective. At the urge of Chairman Wesker, this work was discontinued in favour of finding Alice and domesticating the Undead.
Isaacs' research on the Undead continued, and a test subject - "Ice Hockey" - was captured to test out his antibody hypothesis. By exposing the man to an Alice clone's blood, Ice Hockey developed an immunity to the T-virus as predicted and was seen to demonstrate rudimentary rational thinking comparable to a young child. The unexpected side-effect of this, however, was that the man was now prone to fits of rage and more dangerous than he was before, killing two researchers during the initial experiment. In spite of this setback, Isaacs continued on and recovered more Undead test-subjects without Slater's authorisation, producing an army of "Super Undead".
Las Vegas attack
The day after Isaacs' creation of Super Undead, an extreme burst of psionic activity was detected, traced to the Desert Trail Motel outside Las Vegas, Nevada. Though this was a highly-likely indication of Alice's presence, Chairman Wesker refused to allow any retrieval missions until the Committee could deliberate. Outraged at this thorn, Isaacs fabricated orders from Wesker to justify helicopter transporting Super Undead cargo out to Las Vegas with himself, techs and a security team on board. From a rooftop observation post, Isaacs' team was able to access Alice's visual feed and monitor her combat with the Super Undead. Whether killed by the Super Undead or shut down remotely, Isaacs intended to harvest her blood to continue his research in domesticating the Undead. Isaacs however, totally underestimated Alice, and she quickly discovered the observation post and attacked it, destroying sensitive computer equipment before they could succeed in shutting her down. Unable to stop Alice now, Isaacs opted instead to abandon the mission and escape back to the North American facility. In his escape efforts, however, he was bitten in the shoulder by the last remaining Super Undead.
Mojave massacre and death
Upon return, Isaacs was placed under arrest by Slater, who had discovered the false orders, and was preparing him for execution on Wesker's orders. Isaacs meanwhile injected himself with multiple doses of the Anti-Virus in a desperate attempt to stop the virus' spread, soon learning the virus had mutated and it was no longer able to stop the spread. When shot in the heart by Slater, Isaacs began mutating rapidly and killed him in return before laying waste to the facility. During his rampage, the facility's White Queen supercomputer was able to seal him in the lower levels but predicted he would simply break through the doors in time.
Soon, the facility was infiltrated by Alice, who had tracked his helicopter, and was led to the lower levels by White Queen. The two engaged in battle, with Isaacs demonstrating superior size, strength and regenerative abilities as well as telekinesis. He was ultimately defeated, however, when he stepped out in front of a laser trap.
- This clone appeared to be similar in nature to Alice, "Bad Rain" and the clones of Carlos Olivera and James Shade in that they were clones of real people, but lacked this knowledge. Instead, they acted as Umbrella employees in various functions. This is indicated by the fact that unlike the other Isaacs clone encountered by Alice, this one was clearly subservient to Albert Wesker and the other Umbrella higher-ups instead of being in charge himself or at least believing himself to be. The Umbrella Committee also possessed the power to order his death which they were unlikely to have the ability to do if he were aware of his true identity and was thus in charge.
- Due to the death of this clone, the real Isaacs - Alexander Isaacs- was believed to be dead for years by both Alice and Claire Redfield until Alice met the second Isaacs clone.
- It is unclear how Claire came to know of his death as she departed in Extinction before Alice faced off with him and Alice never mentioned it to her afterwards. However, in The Final Chapter, Claire was aware of Alice killing this clone and asked about it after learning of the approach of what was believed to be the real Isaacs.
- There is a possibility that J. Isaacs was originally meant to be the same character as the Unnamed doctor in the first film. Besides the fact that J. Isaacs was named after the actor of the Unnamed doctor, Jason Isaacs, the character in the first film also functions in a similar mysterious role in the first film that is never explained further.
- Resident Evil: The Final Chapter (2017).
- Resident Evil: Extinction (2007).
- Resident Evil: Apocalypse (2004).