The player starts off heading down an elevator to the facility where they are informed by their boss, the chief investigator, that their findings have not been sufficient. The next night, the player heads down to the facility through an elevator, and Chapter 2 officially begins.
During Night 5 of Chapter 1, Theo informs the player that there's an abandoned underground facility right below the factory, and he says that there is possibly an animatronic down there.