BIOHAZARD VENDETTA is the official novelization of the 2017 film, Resident Evil: Vendetta.
The novel begins with the fallout from the 2013 assassination of President Adam Benford and Neo Umbrella's attacks. The Division of Security Operations is conducting an investigation of American politicians suspected of collaborating with The Family in its bioweapons development, which was so vast that even the current President may have been involved. The DSO is currently on an assignment to investigate Maryland senator Steven Air. During the mission, three agents are killed in a car bombing, which implies even the DSO has been infiltrated. Leon is the sole survivor of the mission, and is left psychologically scarred. Already depressed over having to kill the President - his friend - during the attack on Tall Oaks, Leon goes over the edge and begins to question the point in fighting any longer.
Meanwhile, Chris Redfield is a BSAA observer to the Mexican Army as a platoon is sent to track down Glenn Arias in Iztaccíhuatl and rescue the abducted BSAA agent Cassy White and her two children. Glenn Arias is the alias of a former CIA agent who became a black market bioweapons dealer. With Tricell and Neo Umbrella's influence on the market gone, Arias is now the next big threat. The platoon arrives in Iztaccíhuatl to find a Trevor-style mansion. As they search the residence they fall victim to its traps, or are killed by Zombies left there by Arias as a further trap. As the platoon withers away to just Chris, Arias sets the building alight and prepares to leave. Chris escapes the blaze, and the two begin fighting. However, Arias' martial arts skills outclass Chris. A large mutant human arrives, under Arias' control, with Cassy White and her children, who are zombified also. Arias loses interest in killing Chris, and instead leaves him for Cassy. Reinforcements arrive and save Chris, but Arias and the mutant get away. In a flashback it is revealed that Arias turned his back on the CIA after an attempted assassination attempt on his life on his wedding day. Almost all of his family and friends were killed, including his wife Sarah. Only Diego Gomez -who became the mutant- survived, having shielded Arias from the blast.
In present day Chicago, Illinois, university professor Rebecca Chambers is working with Aaron to create a functional vaccine to a new virus spreading around North America. Thirty corpses infected with the virus have been newly shipped to the lab as samples, and Rebecca is close to completing her work. When the vaccine is completed, the facility is attacked and an airborne virus is released into the room, infecting Aaron but sparing Rebecca. Diego's daughter, Maria, unzips herself from one of the bodybags. Although infected, she is conscious unlike ordinary zombies, and hacks into the laboratory's files for information on the vaccine before destroying the facility. Rebecca is rescued by Chris and his new BSAA team, the Silver Daggers. At a hotel, Rebecca watches news of viral outbreaks in Minnesota and Canada, and is quick to report her vaccine synthesis to Chris. Unfortunately, the United States government is still opposed to BSAA intervention on their soil. As a result, they have no jurisdiction in local counterterrorism affairs. Chris reveals new information they have obtained, which is that the new virus' genome is unusually similar to the Plagas used by Los Iluminados in 2004.
Rebecca and the Silver Daggers head out Colorado in search of Leon, who had previously fought the Plagas when Los Iluminados abducted President Graham's daughter. They find him at a restaurant to be uncooperative due to his loss, while Rebecca suggests they vaccinate themselves for their mission. Chris tries to comfort Leon. Having experienced something similar during the Lanshiang attacks, where he wanted to quit the BSAA, Chris tries to make Leon see that quitting is to allow people to victims to die in vain and it is his duty to keep on going.
The restaurant is being spied on by Arias, who is curious as to Rebecca escaping infection. Intrigued by the woman, he orders Maria to apprehend her, which she does when Rebecca heads to a restroom. Silver Dagger members DC; Nadia and Damien confront her, but are quickly taken down. Leon and Chris are meanwhile distracted by Patricio, a former Los Iluminados cultist and drug dealer, who wishes to help Leon. He is fatally wounded when Diego destroys the restaurant with a gatling gun, and is desperate to give Leon his phone before dying. Leon makes the decision to help Chris when Patrico's daughter tries to ring up.
Rebecca wakes up in Manhattan, wearing in a wedding dress. Arias, knowing her intelligence, describes to her his "a-Virus" creation. It exists in three strains, "Base"; "Trigger" and "Inactive". "Base" creates Zombies, and has spread by fluidic contact through the "Agua" Great Lakes mineral water brand. "Trigger" is an airborne pathogen, which was used at the lab. When someone is infected with "Inactive", they can retain their consciousness and be ignored by Zombies. Arias believes the vaccine Rebecca created will not be effective, and wants to use the antibodies in her blood to force the virus to mutate further. Arias is still embittered by his wife's death, and sees all of humanity to be guilty for it. Taken by Rebecca's resemblance to Sarah, he proposes to her, threatening to have her infected with the a-Virus and ordered to agree should she turn him down. Rebecca refuses to marry him, so he has her sent away to the lab to be infected.
The Silver Daggers are looking through Rebecca's laptop for any information they can find on her location. Leon remembers Patricio's phone, and decides to insert its SD card into the laptop. The team quickly finds out both Arias' location and his plan to disperse "Trigger" over New York. They arrive in the city too late to stop the spread of "Base", with Zombies already flooding the streets. The team splits into two groups, with Chris; Nadia and DC heading into Arias' fortress to apprehend him and Rebecca, while Leon and Damien handle infected dogs while looking for where the virus is to be dispersed. The latter team succeeds in preventing the attack, though at the cost of Damien.
Chris' team finds Arias, who warns him of Rebecca's infected state as Maria shoots DC. Chris follows Arias to a lab and tries to rescue Rebecca, ignoring his warning that she has thirty minutes before the virus takes over. When Rebecca begins to fall ill during the escape, Chris is forced to return to the lab. He is attacked by Diego, but the Silver Daggers succeed in ending their fight in time for them to get into the lab. Chris considers infecting Rebecca with the "Inactive" strain to prevent her becoming a Zombie. He gets into a fight with Arias, followed by he and Leon fighting a mutated Diego. When the two foes are killed, the Silver Daggers leave the building in a helicopter intent on dispersing "Inactive" onto the ground below to end the epidemic. Maria is revealed to have survived, and vows vengeance for her father's death.