The Secret Storage
The button, of course, activates the plant display, which also serves as an entryway to the room beneath the steps. Because most stairwells have extra storage space beneath them, it’s no surprise that this trick door led there.
The plant display, on the other hand, could easily convince someone to believe that there was nothing further to view on the other side. After all, not every stairwell requires a closet beneath it. The majority of the areas below the stairwell do not have such complicated access.