"It has been over half a century since the first incident, which brought the entire mystery together into a complete story. Orchestrated by the former CEO of Afton Robotics, LLC, William Afton Sr., the first incident began in the year 1962 after his employees at his fast food restaurant, the Rat & Cat Theatre, were suspected for public drunkenness; one of his employees in a Rat's costume was playing hide-n-seek with some children when Afton Sr. called him in his office for a discussion about his condition.
Afton Sr. says that he sought too much potential to allow alcoholic beverages in the Rat & Cat Theatre hence decides to fire him. However, the Rat refuses to leave his job, protesting that it is all his life's work, thus he vows to continue his popularity at the Rat & Cat Theatre. Infuriated by the Rat's turndown of his termination, Afton Sr. attempts to pry his costume off, but he ends up shoving him onto his desk, killing him instantly. Another character, Candy the Cat, discovers the Rat's murder and tries to call 991, but Afton Sr. chokes him to death before lying to the police through phoneline about his employees' death by alcoholism. A little girl named Mary Schmidt seems to happen by while playing hide-n-seek with her friends, only to discover his employees' murder which she reported to the police, including her father, the sheriff.
Consumed by the hatred of his company's ever-growing popularity without his approval, Afton Sr. flees to a factory, Circus Baby's Entertainment and Rental, where he sells his soul to devil by undergoing a cyborg conversion self-surgery to become the "Malhare Virus", a computer virus which can control any animatronic he can hack at his own will. Desperate to save his father's company, Afton Sr.'s son, William Afton Jr., succeeds his father as CEO, declaring a manhunt to avenge his employees' death, but when the manhunt started, Afton Sr. vanished and went into hiding in preparations for his return.
25 years later, in early 1987, another incident occurred at Fredbear's Family Diner when a juvenile 17-year-old Terrence "Eggs" Benedict inadvertently murders his younger brother, Christopher, by placing him into the mouth of one of the animatronics. Despite his decaying corpse, Malhare watches the news about the incident at the Diner, believing that Eggs might be useful of his new body.
Meanwhile, instead of receiving a life sentence behind bars, Eggs was placed under community service at Circus Baby's Entertainment and Rental as a maintenance worker. There, Malhare has set a trap for him; he wanted Eggs inside his base of operations, and Eggs obliges. Now, Eggs' main task is to repair the building's gas leaks so that Circus Baby's Pizza World could have its opening date later on, and yet Malhare knows his game. To orchestrate his strategy to his minions, Malhare activates the animatronics and sends them to his current positions. Then, when the time is right, they kidnap him. Eggs is then brought to the Scooping Room where his skeleton was viciously removed, enabling Malhare conceal himself inside Eggs' corpse to finally emerge back into the world to start his bloody rampage.
In late 1987, Freddy Fazbear's Pizza has made its official grand opening, along with Afton Robotics, LLC renamed as "Fazbear Entertainment, Inc." to honor it. That is when Malhare infiltrated the newly opened pizzeria in a golden Bonnie suit, luring four more children to a Parts & Service Room where he kills them and stuffs them in old animatronic suits, replacing their souls with his virus to control them under his command. The company's board suspects that the four children might be in great peril beyond their disappearances, so they sent a security guard named Jeremy Fitzgerald to check on them for a weeknight. Eventually, enough evidence has been brought to the Washington County officials, believing that Malhare, whom he suspected as Afton Sr., has taken the form of the now deceased Eggs Benedict to achieve vengeance. A full-scale manhunt was then ensued to capture Malhare, but to no avail.
Five years have passed since the failed second manhunt, a college graduate named Mike Schmidt has been championed by Afton Jr. to spend five nights at the rundown Freddy Fazbear's Pizza to ensure Malhare doesn't hack the animatronics after him as well. Five nights have passed, and Mike came out victorious on his first week at his new summer job at Freddy Fazbear's Pizza. Angered by his minions' lack of progress, Malhare dismantles the animatronics and prepares to go into hiding again when the spirits of all five children he murdered appear, intent to get revenge on him for all his crimes against humanity itself. As the spirits close in, Malhare discovers an old animatronic suit down in the basement. However, as Malhare hides in the suit to protect himself from the spirits, its faulty spring-lock mechanism fails, and the latter is crushed as the spirits fade away, leaving their killer to seemingly bleed to death. At the start of his second week, Mike discovers that the format of his shift has somehow changed until he realized, when he investigates the basement, that Ennard has met his seemingly utter defeat. Afton Jr. was also relived that the mystery was finally over after 30 years of failed investigation, and yet Fazbear Entertainment was glad to be rid of Ennard for good.
Thirty years have passed since the case of the "Five Missing Children" has been closed, an amusement park was built around the abandoned Freddy Fazbear's Pizza, where the owner of the park sought to buy the rundown pizzeria, thus "Fazbear's Fright: The Horror Attraction" was born to honor the events Fazbear Entertainment went through over half a century ago. Little do guests of Fazbear's Fright know that there was an ancient relic, which they call "Springtrap", hiding in a boarded up Safe Room. Eventually, after accidentally bringing himself back to life by Malhare, Springtrap fled Fazbear's Fright for a safer hideaway until he comes upon a newly constructed family entertainment center, known as "Freddy Fazbear's Mega Pizzaplex", and decides to take control of the place, placing the newly built location under temporary lockdown until an opening date was declared. A security guard named Vanessa was sent to investigate the hiatus, but she vanished. Little did Vanessa nor Fazbear Entertainment know that Malhare was still alive hence had a few tricks up his sleeve. Gregory Afton, the grandson of William Afton Jr., believes that someone was trying to take over the entertainment center, and having lost a bet from his friends in a web chat, he goes there one night to help turn Freddy Fazbear's Mega Pizzaplex back to normal.
The Malhare Virus lives, and this time, it will not only be to shut down Fazbear Entertainment for good - it will be...for revenge."