Her first clue that something is wrong comes when she gets lost in the palace gardens.
Getting lost in the palace gardens is not that unusual. Everybody does it. But she grew up here, and she would've thought she knew the place better than almost anyone. That's the stone bench she chipped a tooth on when she was a very fast and reckless toddler; that's the tree that still has scars in the not quite recognizable shape of a flower from when she was eight and tried to carve her name in it but found that her creative ambitions had badly outpaced her skill. And yet, a few turns down the winding path through the beds of ornamental roses, she ducks under an ivy-laced arch and suddenly finds that nothing about her surroundings is familiar.
The little nook beyond the arch is nothing special. There's a screen of tall hedges all around, and a tree in the middle to shade the bench beneath it, and it smells like home—like home with a hint of roses—and, when she takes a few tentative steps toward the tree, she sees that there's a scraggly scrap of ribbon tied around one of its branches. She should know that ribbon. It's just the right shade of blue to have come from her very own hair, a year or two ago when she used to wear her hair tied up with pretty blue ribbons. But she can't remember ever seeing it before, or the tree, or the bench, or the hedge. It's like she stepped onto the open pages of a storybook and into the imaginary lands depicted there, as far from home as it's possible to go.
For what feels like a very long time, she stands frozen, staring blankly at the ribbon in the tree. Then she turns around, and the blankness somehow follows her out. Even though the little circle of hedges was only a single step away from familiar ground, even though she must have walked this very path not two minutes ago, she has the unshakeable sense that she has never seen these roses before in her life.
She closes her eyes and tells herself very firmly that she is home and she is not dreaming. When she warily cracks a lid, the roses still look just as inexplicably alien. She ends up having to navigate back to the castle by painstakingly drawing a map in her head of every turn she takes, learning the whole rose garden over again until she finally stumbles across an exit; and then, as soon as she's standing on flagstones again, the sense of familiarity snaps back into place as suddenly as it first disappeared. She turns around and looks into the rose garden, and it's the same old rose garden it's always been, the same old rose garden she's known like the back of her hand since she was two years old and hiding in thornbushes to escape a nanny.
She doesn't set foot in the rose garden again that month.
There are other blank spots, scattered around the palace and its grounds. Not all of them are adorned with her very own hair ribbons, but there's a corner in the back of the library with the words IRIS WAS HERE scratched into the side of a shelf, and a spot in the attic, curtained with childhood bedsheets, dotted with tiny Iris-shaped handprints in blue and purple and white. These are her places, places that should mean something to her, places where she must logically have spent some time. But something has taken them away from her. Something has pulled treasured pieces out of her memory and left ragged voids in their wake.
Well then. First of all, she needs to find out what could possibly have done such a thing. If it can be fixed, then she'll fix it. If it can't... then things may get a little more complicated.