Five Nights at Freddy's begins with Mike Schmidt listening to a voicemail from his unnamed predecessor at the start of his first shift. Similar messages play on the following nights, in which the employee tells Schmidt about the restaurant and its history. The security officer explains that the restaurant's four animatronic characters – Freddy Fazbear, Bonnie, Chica, and Foxy – are allowed to become mobile at night due to their servomotors locking up if they are left off for too long. He warns Schmidt that if an animatronic encounters a human after hours, it will mistake them for an animatronic endoskeleton and will place the human into a spare mechanical suit, killing the person in the process.
The player is indirectly told about disturbing events in the restaurant's history. One of the voicemails mentions "The Bite of '87", an incident which is implied to have led to the loss of a person's frontal lobe and forced animatronic mobility during the day to be prohibited. Newspaper clippings viewable through the camera feeds reveal that a man reportedly lured five children into a back room and killed them. Although the suspect was arrested, the children's bodies were never found. The restaurant later received complaints that the animatronics began to emit foul odors while blood and mucus leaked from their eyes and mouths.
On the fourth night, the voicemail implies that Schmidt's predecessor was killed by an animatronic while recording the message. The final message on the fifth night only consists of garbled sound. Schmidt receives paychecks after the fifth and sixth nights. After completing the sixth night, the player is given access to a seventh "custom night" where they can manipulate the AI difficulty of the animatronics. Upon finishing the seventh night, Schmidt is fired.
