This first quarter of the book beautifully builds up the character of
Kate, a girl who has seen some hardship but seems comfortable in her
own skin, and is nothing if not determined. Still: she's always
seeking, and for all the hours she spends watching these still have
never led to anything, and she is no more a girl on the verge by the
end of this section of the novel than at the beginning.
The second part of the book jumps ahead to the end of 2003, during the post-Christmas shopping period at the Green Oaks Shopping Center. New characters are introduced: Kurt, a security guard on the night shift, and then Lisa -- Adrian's younger sister, mentioned in little more than passing in the first section -- who is a deputy manager at a huge music store in the mall. But most conspicuous is Kate, absent except in a few memories: she disappeared some twenty years earlier, and her disappearance remains a mystery. There were: "No witnesses, no sightings, no body".
Or so it seems, anyway. But little girls don't simply disappear. Wisely, however, O'Flynn does not focus on the 'mystery', but rather on the void that was left -- and she does so all the more effectively by focussing on these two characters whom Kate's disappearance touched more or less only peripherally.