One of Umbrella's leading scientists, he was responsible for much of the research that was conducted on Project Alice. When it was discovered that Alice's dna had successfully bonded with the T-Virus, she was confined to a secret laboratory in the Raccoon City Hospital, where Isaacs injected her with more doses of the virus, causing her to develop superhuman abilities, such as hightened strength and agility as well as rapid healing abilities. Alice managed to escape from Raccoon City along with several other civilians before it was hit by a nuclear missile to contain the T-Virus outbreak, but the explosion caused the helicopter that Alice was fleeing on to crash into the surrounding forest. Dr. Isaacs and his team managed to extract Alice from the helicopter wreckage, and they took her to Umbrella's facility in Detroit, where Alice was restored by being pumped with yet more T-Virus. This time, Alice regained her senses so quickly that she attacked Isaacs and his team and left the facility, learning that she had also developed telekinesis, which she used to kill a security guard who was watching the surveilance videos. Shortly after leaving the facility, alice was picked up by her friends from Raccoon city, who were disguised as Umbrella officials.
But Isaacs was still not finished with Alice - he had embedded technology inside her body which enabled Umbrella's satallites to track her. During this time, the T-Virus outbreak had spread beyond even Umbrella's control, and most of the world's population had been reduced to undead zombies. Alice, knowing that she was being tracked by Umbrella, abandoned her friends and wandered off on her own so that they would not be targeted by Umbrella. Dr. Isaacs had relocated to Umbrella's isolated facility in the Nevada desert, and had managed to salvage dna samples from Alice, which he used to create many clones. Isaacs tested the alice clones in a training area in the Nevada facility, and discovered that each new clone was inheriting the memories of the previous Alice. He also hypothesised that he could create a potential cure tot he T-Virus, or at least use Alice's blood to keep the already infected zombies under control and use them as a work force to regain order on the surface world.
However, without the original Alice, Isaacs' work produced unstable results. He tested a sample of one of the clones on a captured zombie, and it briefly displayed some sense of reasoning, but it quickly became aggressive and turned against the scientists. Furthermore, it now possessed greater strength and speed than a regular zombie. Isaacs decided that this new breed of zombie would be useful in capturing the true Alice. When the Nevada Facility's computer system, White Queen, detected the location of the true Alice via Umbrella's satellites, Dr. Isaacs created more of these advanced zombies and sent them out to attack Alice and a convoy of survivors she was helping in Vegas. During the struggle, Isaacs' technical team managed to shut down Project Alice, and she became incapacited. Isaacs waited for the advanced zombies to kill Alice in this state, so he could extract her blood. Unexpectedly, Alice managed to resist Umbrella's sensors and she rescued the remaining survivors before heading towards Isaacs and killing off his team. Isaacs rushed to his helicopter to escape, but on the way he was bitten by one of the advanced zombies. the pilot killed the zombie and carried Isaacs back to his lab, where he tried to cure himself with the anitvirus. However, the antivirus was not strong enough to stop the infection from this new bite from an advanced zombie, so Isaacs began injecting himself with all of the DNA samples he had taken from the Alice clones.
Captain Slater, who was in charge of the Nevada Facility's military force, tried to kill Isaacs and assume control over the complex, but Isaacs had mutated into a powerful creature and killed slater and the rest of the soldiers and scientists int he facility. The White Queen activated her security system and managed to contain Isaacs in the lower levels of the facility, but as he was growing stronger, he would soon be able to break out eventually. Eventually, Alice arrived, and with the White Queen's help, she descended intot he facility and fought against Isaacs. Isaacs knocked Alice into one of the training rooms, which had been set up with a laser defence system. He was about to kill Alice, when one of her clones had awoken and activated the lasers, using them to slice Isaacs into pieces.
With Isaacs dead, Alice assumed control over the Nevada facility, and gathered all of her clones into a single front that would head out to confront the rest of the Umbrella facilities and put an end to their evil.