The question had been building in her for days, and it finally escaped her on a night when the rain outside the train windows fell harder than she'd ever seen it fall.
"Are you real?" Mira asked.
"Does it matter?"
"Yes." She said it without hesitation, surprising them both.
She looked around and realized, for the first time, that the train was entirely empty. There were no passengers anywhere — not the vague shapes she'd half-noticed in other carriages on other nights, not even the sense of other lives happening somewhere beyond this one conversation. Tonight, it was only the two of them, and the rain, and the dark rushing past outside.
On the seat beside Aiden lay an old ticket, its edges soft with age, its ink faded to a ghost of itself.
"This is old," Mira said, picking it up carefully, the way you'd hold something that might crumble.
"Very."
She looked at the date printed along its edge, and something in her went cold and still.
It was the date of the accident.
"Why do you have this?" she asked, her voice barely above the sound of the rain.
Aiden said nothing. He looked at the ticket in her hands rather than at her, and his silence had a weight to it that told her, more clearly than words could have, that she was standing at the edge of something.
Another memory surfaced then, unbidden, pulling her under before she could brace for it.
"Mira, don't go yet."
"Why?"
"Just wait for me."
She came back to herself slowly, blinking against the train's dim light, and looked at him with new understanding dawning in her eyes.
"You were there," she said.
"Yes."
"You knew my family."
"Yes."
She made herself say the next words, though every part of her resisted them.
"You died."
"Yes."
"Then why are you here?"
"Because you kept looking for me."
"I didn't even remember you," she said, and it came out almost like an accusation, aimed as much at herself as at him.
"Some part of you did," Aiden said gently.
"It never really stopped."
And in that moment, sitting across from a boy who had died years ago and somehow never left her, Mira finally understood what Platform 0 actually was.
It was never a station for trains.
It was a station for unfinished goodbyes — a place that existed only for as long as someone needed it to, holding open a door that grief had never let close.
"There is only one journey left," Aiden said quietly, as the train rushed on through the dark.
"For who?"
"For me."