At first, she occasionally disappeared, taking her toothbrush and a few changes of clothes.
She was straight out of Hogwarts back then and Neville would worry and refuse to sleep until she was back. He'd waste away for a week every few months until she came back and he pretended that everything was alright. She'd reappear, muddy but full of stories and joy and he couldn't possibly tell her not to leave his side ever again when she's like this.
He's not someone you'd want to spend forever with, so he doesn't force her.
After a few years, she disappears for a month.
Neville's Auror training kicks in and he finds himself tracking her as if she's a stray Death Eater in hiding. As soon as he realizes that, he feels sick to his stomach. But then she comes back with a rough draft of a book on magical creatures and he just smiles at her encouragingly when they lay in bed that night. He doesn't sleep, instead watches her sleep and makes sure she's not going anywhere. He thinks about the ring his Gran gave him a few months prior and how ready to propose he felt then. Now he thinks he can't possibly tie her down.
Not to him.
It happens every now and again, and two weeks after he talked himself into proposing and did it, she leaves a note in place of herself in their bed. She says she'll be back and that it's just a quick trip to the US. Neville's unsure whether he should immediately push their wedding back. He eventually does, after two months of waiting.
He gets letters every now and again, short and sweet and always full of love. They warm his heart but he's still unsure if he's doing the right thing after all.
He's twenty-six now and maybe a bit too old for this uncertainty of whether she will ever come back or not.
But as winter turns to spring she comes back like a turtle dove, half a year after she disappeared and with a bulging stomach.
He knows he shouldn't doubt her. And it is less doubting her and more doubting himself that makes him worry. Because he wouldn't blame her if she did.
Not when she's with him.
So he doesn't ask and since she never says otherwise, assumes it is his firstborn child growing inside her. Or rather barely growing and just waiting to get out into the world.
He asks if she knew about it when she vanished. She says no. He still feels a bit robbed out of watching his fiance's – his fiance's – pregnancy as it happened. He's grateful she came back when she did though and not years down the line. She wasn't cruel, just didn't think much of things others found incredibly valuable.
And since their wedding was postponed to July, he just prays that she'll stay until then. His Gran would probably die if she didn't.
A month later she's giving birth and Neville holds her hand at St Mungo's as her forehead creases and teeth clench. He wishes he could feel the pain instead of her, remembers the times Carrows crucio-ed her back at Hogwarts and feels the same dread building up as he did then. Because he's as useless as he was back then, unable to stop it.
She names their daughter Alice Pandora and he's ready to forgive it all when he looks into her little face. Because she's given him the most beautiful gift he could ever wish for, a part of herself that he fell in love with instantly.
Alice is less than two months old when she disappears again and there are tears running down his cheeks when his daughter cries for her mother. He's feeling as helpless as she is, but he has to pull himself together. Cause Alice deserves better.
He thinks their wedding is of course not going to happen and of course she shows up a few weeks before the date. It's been only two weeks without her but Neville was prepared for a longer wait, already thinking about what Alice's life was going to look like with her continuously absent mother.
It's the first time he raises his voice, the first time he calls her out for leaving everyone behind – because it's no longer about him. Because Alice deserves better.
He calls off the wedding. He leaves the flat with Alice in his arms and moves back to Gran's. When Ginny floos him she doesn't even try to talk him out of it.
They knew, they all knew it wasn't going to end well. Despite that, they never told him.
Alice grows up fast and he knows she notices it whenever she visits. She never tried to take her away from Neville before and she certainly isn't now, because they both know her lifestyle isn't child-friendly. But she visits fairly often and always brings her interesting gifts from her travels. And Neville's heart breaks when she looks at their daughter and knows that she's missed the first word, the first steps, the scraped knees and even such mundane things as haircuts. Whenever it happens Neville is willing to work things out, if only for their sake. Because he loves them both more than life itself.
But then there are moments when Alice's sick and his Gran is away and he floos her in the middle of the night because he's been called to work and it turns out she's gone off without a word once again. There are moments when Alice needs her and she's not even an available option.
And Neville wants to hate her then, but he can't. Because it was him who tried to ground her when she wasn't destined to be.
And he didn't succeed, because he's not enough to stay grounded for.
But Alice is. She's worth every galleon in the world, worth every sleepless night, every hardship he faces. He'd move mountains for her, die for her a thousand times over.
And if Luna won't stay grounded for their daughter, he's going to work twice as hard to make sure Alice never wishes for her to. Because he knows it's the one wish he can't grant her.