I've revised this somewhat, thanks to my beta, jacquez.
"Harry? It's cold outside."
"Is it?" He turned to face Neville, but there was nothing in his eyes. He didn't seem to see him at all. "Funny, that."
"Yeah. It being December and all, and us in Scotland." He wrapped the cloak he brought around Harry's shoulders. Harry didn't notice that, or that Neville never did take his hands away. "Maybe you should come in." Snow swirled around them, making the castle an ominous dark shape in the distance.
Harry shrugged. "It doesn't matter. Not like this is going to hurt me now, is it? I have a *destiny*, don't I? Kill or be killed, or maybe both? So I'm not going to die of pneumonia or anything." Neville could have gagged on the bitterness in Harry's voice. So that what he was thinking when he wandered alone.
His shoulders were bony under the cloak and the school robe. Neville had watched him barely eat for months, except when Hermione nagged at him, much as he'd watched him just stand outside the castle for months - the time since they started their sixth year. Harry was only alive on the Quidditch pitch these days, or when he taught the DA.
"How do you know that?" Harry frowned but didn't say anything. "How do you know that you can't be hurt? Destiny's a funny thing, Harry. I mean, from what you said, it was almost me who could be killing Vol…Vol…Voldemort. Prophecy works as well for the two of us, except he chose you. Not that I envy you the choosing, but. It's like I'm a spare, you know? And, I'd take it from you if I could, even if the thought gives me nightmares."
"That's what he called Cedric." His voice was so low, Neville could hardly hear it. "He said, 'Kill the spare' and he killed him. His voice is so cold. Colder than this, than this snow." He looked up, and this time Neville knew he saw him. "But you are not a spare, Neville. You're too brave for that. I…I blunder into things without thinking, which is not bravery, but you go in with those eyes wide open. You're a true Gryffindor." He pulled the cloak closer around his body, as if finally feeling the wind cut through him.
"That's not bravery. It's just doing what has to be done." Neville smiled. "But you'll do it, Harry, and you'll survive. And if I can help in anyway, I will. It doesn't matter what happens to me."
Harry looked at him. His eyes were very green behind his glasses. "Yes, it does. It does more than anything I could say." He bit his lower lip for a moment, and then let it go. His mouth was very red, bright against his winter-pale cheeks.
Neville's heart turned over. He leaned forward, his hands still on Harry's shoulders, and wondering just when he'd gotten taller, kissed him on that mouth. Harry did nothing at first, but then his lips softened and moved and they wrapped their arms around each other, and suddenly it was warm in the middle of the snow of a Scottish December.
And Neville took him by the hand and led him back inside to a warm fire and food nicked from the kitchen.