The game consists of five nights, increasing in difficulty, and completing all five unlocks an even more challenging "Nightmare" night. Several low-resolution minigames are hidden within the main game; completing all of them unlocks the game's "good ending" and grants access to bonus content that includes a cheat menu.
If the player completes the "Nightmare" night, they will unlock the cheat menu. The cheat menu offers a range of options, including a mode to make the animatronics act more aggressive and therefore make the game harder, depending on the player's skills. Other cheats include a radar and the ability to make nights faster.
Plot
Set thirty years after the events of the first game, the player assumes the role of a newly-hired employee at Fazbear's Fright, a horror-themed attraction based on the unsolved mysteries of Freddy Fazbear's Pizza, constructed using paraphernalia salvaged from the original restaurants. During the week before the attraction is scheduled to open to the public, the player must watch over the facility from the security office during their shift (12:00 A.M. to 6:00 A.M. game time), using a network of surveillance cameras placed in the rooms and air vents. In addition, the player must monitor the status of three operating systems - cameras, audio and ventilation - and reboot them whenever they begin to malfunction. Camera problems cause the video feeds, already poorly lit and distorted, to become totally obscured by static. If the ventilation fails, the player's vision begins to black out. The player may also see phantoms of animatronics from the previous games; these can cause system malfunctions, most commonly in the ventilation, but cannot directly harm the player.
After the first night, the staff at Fazbear's Fright uncover an older deteriorated, rabbit-like animatronic which they nickname "Springtrap"; The player must now prevent it from entering the office and attacking; if this happens, the game ends. The player can seal off the air vents at certain points to block its progress, but cannot seal the door or air vent that lead directly into the office. The audio system, when functioning properly, can be used to play sound effects that draw it away from the office. Ventilation malfunctions can cause the player to hallucinate seeing more than one Springtrap on the cameras.
As the nights progress, the player hears a series of instructional cassette tapes (similar to the telephone calls from the first two games) that instruct employees how to operate the "Spring Bonnie" suit, which can function as both an animatronic and a costume for humans. However, later tapes discourage usage of the suit by employees due to a series of fatal accidents involving the failure of the suit's spring-lock mechanism. Low-resolution minigames between nights hint at the restaurant's troubled past, with the first four nights' minigames depicting the original animatronics following a dark purple animatronic before being violently disassembled by William Afton, previously seen in the minigames of Five Nights at Freddy's 2 as the man responsible for the various murders that occurred throughout the franchise's fictional history. In the fifth night's minigame, the ghosts of the five children who inhabited the animatronics corner William Afton, who attempts to protect himself by hiding in the "Spring Bonnie" suit. However, the suit's faulty spring-lock mechanism fails, and the man is crushed as the children fade away, leaving their killer to seemingly bleed to death.
Unlike the previous entries, Five Nights at Freddy's 3 contains two endings, depending on whether the player has found and completed all of the hidden minigames within the main game. Some of these are only available on specific nights, while others can be accessed during any night. The "bad ending" is attained from completing the game without completing all the hidden minigames, and shows a screen depicting the heads of the five animatronics from the first game with lit-up eyes, implying that the animatronics are still possessed. Completing all the hidden minigames before completing the game earns the "good ending", which is the same screen as described previously but with the animatronics' heads turned off, with one head disappearing, presumably Golden Freddy. This implies that the children's souls have finally been put to rest.
Completing all five nights unlocks a bonus night, "Nightmare", which boosts the game's difficulty, similar to "Night 6" in the previous titles. While playing the mode, an archived recording states that all Freddy Fazbear's Pizza locations' safe rooms (an additional emergency room which "is not included in the digital map layout programmed in the animatronics or the security cameras, is hidden to customers, invisible to animatronics, and is always off-camera.") will be permanently sealed, instructing employees that they are "not be mentioned to family, friends or insurance representatives." When this night is completed, a newspaper clipping reveals that Fazbear's Fright was destroyed in a fire shortly after the events of the game and that any salvageable items from the attraction are to be auctioned off. However, brightening the image reveals Springtrap in the background, which suggests he somehow survived, leaving his fate unknown.
