Wesker is based on the character of the same name from the Resident Evil video games, though there are notable differences between the two. In the games, Wesker worked for Umbrella for a time and then betrayed the company in order to pursue his own goals. In his quest for power, he turned to bioterrorism and almost destroyed the entire planet with an engineered virus.
Resident Evil: ExtinctionEditWesker makes his first appearance in the Resident Evil film series in the third film, Extinction. He is portrayed by Jason O'Mara and has rather little screen time. He appears via hologram in a conference with Umbrella's other executives and orders Dr. Alexander Isaacs (actually a clone of the real Isaacs) to focus his efforts on domesticating the Undead. However, Isaacs goes behind the chairman's back and develops enhanced zombies with which to hunt down the renegade Project: Alice.
Following the death of Isaacs and the destruction of Umbrella's Nevada base, Wesker decides to personally supervise all of Umbrella's main research projects from then on at the company's underground headquarters in Tokyo. His meeting with the executive board is interrupted by a transmission from Alice, who warns Wesker that she's coming after him and is bringing an army of clones with her.
Resident Evil: AfterlifeEdit
In the fourth film, Wesker is portrayed by Shawn Roberts. When Alice and her clones invade Umbrella HQ, he displays great callousness when he shoots his security chief for questioning his order to flood the base's upper levels with nerve gas. Wesker is not a typical executive and doesn't run and hide from danger, as demonstrated when he uses his impressive marksmanship skills to kill several Alice clones as they dive down into the base's main control center. As the clones overwhelm his troops, however, Wesker makes his escape aboard a V-22 chopper and activates the base's self-destruct system, imploding the entire complex - as well as a sizable portion of Tokyo - and killing all of Alice's clones. The real Alice, however, managed to sneak aboard the chopper before it took off and holds a gun to Wesker's head. Unfazed by her threat, Wesker quickly wheels around and jams a syringe into Alice's neck. The hypodermic is filled with a serum that destroys the T-virus cells in Alice's body, removing her superhuman powers. As Wesker gloats, the chopper flies toward a mountain and Wesker is too little too late to stop it before it crashes. Alice barely survives the crash and Wesker is presumed dead.
Five months after the crash, Wesker appears alive and well aboard the Umbrella ship Arcadia. He apparently survived because he had injected himself with the T-virus prior to Alice's attack on Umbrella HQ. Like with Alice, the virus did not turn Wesker into a zombie but granted him superhuman abilities such as enhanced strength, speed and rapid healing. However, Wesker had trouble keeping the virus in check and had to struggle to maintain control of himself. He started feeding on the flesh of the Arcadia crew in order to maintain a balance, so to speak. When he started eating his crew, of course, most of them abandoned ship, leaving him alone on the ship with thousands of captured people being held for experimentation.
Toward the end of the film, Alice and the Redfield siblings encountered Wesker on the Arcadia. Wesker believed that if he ingested Alice - who had adapted to the T-virus on a genetic level - then he could regain full control of his body. A fierce struggle ensued between Wesker, Alice, Chris and Claire, with Wesker's new superhuman powers giving him the clear advantage. At one point in the fight, Wesker's new lackey Bennett Sinclair stabbed Alice in the arm with a combat knife. While Alice stood stunned and tried to get the knife out, Wesker lunged at her, a set of mutant mandibles emerging from his mouth. Alice managed to pull the knife out and then stabbed Wesker in the head as he lunged at her. K-Mart then knocked out Bennett and threw Alice's coin-loaded shotgun to her. Wesker was not so easily killed, of course, and pulled the knife out of his head before making another lunge at Alice with his mandibles. Alice aimed her shotgun at Wesker's mouth and fired, knocking him back again. Even after having a gaping hole blasted through his head, Wesker still wasn't finished and tried to get up, only for Chris Redfield to step on his chest. Both Chris and Claire then pointed their pistols at Wesker and emptied all of their bullets into him at point blank range.
Wesker's T-infected body proved to be near impossible to kill, however, and he even survived multiple point blank shots. When Alice, Chris, Claire and K-Mart exited the Arcadia control room, they locked the door behind them and left Bennett trapped inside. Wesker reanimated again and devoured Bennett before making his escape, activating the ship's self-destruct device: a Purge bomb like the one that destroyed Umbrella HQ. When Wesker boarded his chopper and made his getaway, he heard a beeping inside his aircraft's cabin and noticed that Alice had already removed the Purge bomb and planted it on the chopper behind the parachute racks. Wesker's eyes angrily glowed red behind his shades moments before the bomb detonated, destroying his aircraft.
Moments after the implosion, the dust cloud where the chopper was can be seen from a distant angle, as well as what appears to be a parachute, implying that Wesker was able to escape in time.
Resident Evil: RetributionEdit
It turns out that Wesker did indeed escape from his chopper. However, his role in the fifth film is less antagonistic. When Alice meets Ada Wong inside Umbrella Prime, she reveals that Wesker is no longer in control of Umbrella. Wesker then makes contact with Alice, revealing how the T-virus managed to spread across the world and that Umbrella is now under the control of the Red Queen, the artificial intelligence that Alice thought she had destroyed back in the Hive in the first film. Wesker manages to hack several systems, allowing his strike team to enter the base and Alice to escape.
When Alice and co. escape from Umbrella Prime, they arrive in Washington D.C. which is overrun with Undead and various T-virus monsters. Wesker has taken charge of a resistance group that have barricaded themselves in the White House and are fighting to prevent humanity's extinction, though the former Umbrella Chairman likely continues to plot and scheme for his own selfish gains. When Alice meets with Wesker in the Oval Office, he injects her with a serum that swiftly restores her lost superpowers, as she will surely need them in the inevitable final confrontation with the Red Queen. Alice still views Wesker as responsible for everything that's happened and promises that she will kill him one day.
Resident Evil: The Final Chapter Edit
In The Final Chapter, it is revealed that Wesker's position as Umbrella's Chairman was merely temporary and that he was filling in for Alexander Isaacs. He had infiltrated the Anti-Umbrella Resistance and arranged the destruction of the White House, leading to the slaughter of the resistance. While Alice survived the assault, she is contacted by the Red Queen who informs her that Wesker has retreated to the Hive in Raccoon City where he is safeguarding Umbrella's executives in cryo-stasis as well as an airborne variant of the anti-virus.
As Alice and her allies venture into the Hive, Wesker assumes full control of the facility's defences himself, activating several traps that kill off Alice's allies. Wesker also awakens both Isaacs and Alicia Marcus from stasis in order to oversee the final stage of Isaacs' plan to cleanse the Earth of humanity.
Alice eventually reaches the lowest level of the Hive where she finds Isaacs, Alicia, and also Wesker who is holding Claire Redfield at gunpoint. After Isaacs reveals the details of his plan and how Alice is just a clone of Alicia, Alicia then decides to take action. With her authority as co-owner of Umbrella, she fires Wesker, thereby authorizing the Red Queen to take action against him. The Red Queen activates a blast dor that severs Wesker's arm, leaving him bleeding on the floor. As he lies bleeding to death, Alice places a detonator in his remaining hand that will trigger the explosives planted around the Hive. Alice then leaves with Claire to pursue Isaacs who tries to flee with the anti-virus, leaving Wesker and Alicia alone. Eventually, Wesker bleeds out and drops the detonator, triggering the explosives and destroying the Hive, including the members of Umbrella High Command still in stasis.