When she thinks about it years later Carrigan haunts her. Not in a literal sense of course—she crossed over right before Kat's eyes—but in her mind sometimes she catches the smallest glimpse of guilt that she was in some way responsible. Carrigan was greedy and devious but Kat doesn't know that she really deserved to die completely. Kat wonders at times whether they could make more of Dr. McFadden's concoction, his magic life-giving potion. She had dreams about breathing in the filthy, miraculous soot from the Lazurus.
It's not just so that she could have finished out high school with Casper.
Her feet dangle precariously over the edge of the lighthouse. It doesn't scare her anymore; in fact Kat barely notices the cold rush around her skin. Her shoes sit neatly by her hip, socks stuffed inside them, on the brim of the roof.
"Do you have to stay here?" she asks, her voice battling against the wind.
Casper shrugs, floating by her shoulder. "I've never had anywhere else to go."
Kat turns her face to look up at him. The salty breeze stings her cheeks and her eyes water as she tried look at rather than through him. It's too easy to see the stars shining through the gauzy material that forms his body.
"You could come with me," she suggests.
She doesn't want to go to college without him.
Her dad has tried everything he can think of to make Casper cross over. At first he was genuinely just attempting to help a lost soul. That was his job after all. Kat thinks that maybe he feels a little guilty for stealing Casper's second-chance at humanity... but he never talks about that.
None of them do.
Now it seems more like a personal grudge match between her father and her best friend. Her dad always wished that she would become more involved in his work or at the very least more accepting, but when she finally shows an interest he disapproves. Of course he still likes Casper, he's even grown fond of the three insufferable uncles who still taunt Kat at every turn, but she knows he doesn't like her spending time with a ghost to the exclusion of living breathing people.
He asks her about her school day and the girls that she talks to in class. He wants to know who she sits with at lunch. He pesters her about never having people over for study dates or sleepovers.
Ultimately her father loses the battle an although she's only weeks away from graduating high school Casper is still very much present at Whipstaff. Kat is outwardly happy about his company. She tries not to acknowledge the tiny, secret part of her that resents Casper.
She has kissed boys and dated a little and through it all she can't seem to stop thinking of him, doesn't want to be without him. She knows that it's unhealthy, clinging to something so incorporeal, but she can't help it.
That only leaves her one option for moving on and he's being stubborn about going into the light.
He never grows up. He doesn't have memories or hormones. Kat finds herself torn. She wants so badly to let him keep her but she can't escape biology and she is growing up. He doesn't really know any different but she begins to long for the feel of flesh on flesh. She dreams of his reflection. She remembers the twelve-year-old boy who danced with her at that first Halloween party and wonders what he would look like now.
She thinks of her mother and tries to understand why they're not allowed to meet anymore when she's clearly still around somewhere. More than anything though Kat obsesses over the reasons Casper could have for refusing to cross over. She can't imagine now that he can remember his life and his uncles are relatively civilized... what unfinished business could be left?
She's no scientist—the Lazurus has been used successfully for the first and final time already.
He hovers by her, resting on the warm breath escaping her mouth. Kat has become used to his closeness while she sleeps. She doesn't know if Casper sleeps—if he can, if he needs to—but she knows that while she sleeps he'll be a light breeze above her bed. The slight chill doesn't bother her anymore.
"Casper?" she mumbles softly, nearing unconsciousness. "What's your unfinished business?"
She falls asleep before he can softly answer, "You."
He has a feeling that one day he will forget her, maybe not until years after she has left him... but eventually. One day he'll come across an old photograph of her that's still tucked up in the attic and he will remember. It will be like fitting his heat into an exact plaster cast.
When she dies—and she will die one day, everyone does—he doesn't expect her to have unfinished business. He definitely doesn't pin hopes on them ever being together in the whatever you cross to. He does fully expect to linger in Whipstaff for however long the building can remain standing.
He wonders if maybe, when all that's left of her is rubble, he'll be able to let go.