CW: Suicide references/imagery
Ford watched Macnair work through it, recognizing the signs in his expression of someone working through trying to compartmentalize a fear. While Ford watched, he turned the boggart's form over in his mind. Nothing to do with the pistol itself, he didn't think; if Macnair was afraid of death by bullet wound then the person holding the gun could have been anyone. Unless — he was afraid he might use it on himself.
Ford was jumping to conclusions, he knew that. And he knew that this particular conclusion probably had more to do with Ford's month and with his newfound anxieties about Noble than with anything Macnair had said or done. Still, once it had occurred to him it stuck in his mind, and he couldn't seem to see any other interpretation of the boggart. There probably were other interpretations, and he just couldn't grasp them — he didn't know Macnair that well — but all the same his stomach did a little guilty flip. Ford should have stepped in and taken the boggart on himself, because not everyone was capable of facing up to their fears. He'd started to move to do so, but just as he lifted his foot Macnair cast. The spell took, and the boggart swirled away.
Ford swallowed, still feeling guilty for making Macnair face that when he could have stopped him. "Good work," he said, and reached out to squeeze Macnair's arm in what he hoped was a vaguely reassuring way. There was a lot he tried to communicate with the small gesture.
It's over, you survived, and you're not alone. All of the things he would have rather said to Noble, in the aftermath of the dinner party, instead of everything else they'd said.
The boggart was still there, little more at the moment than a whisp of smoke. Ford knew it would rally though, and he stepped to place himself squarely between the boggart and Macnair, his free hand stretched out almost protectively at his side. The boggart reformed and, perhaps predictably, there was his brother staring back at him. Noble's eyes were wide with surprise, maybe with fear, but he was very still. Except for the white foam leaking from his mouth.
Boggarts had shown him his brother dead before, but it hadn't happened for a while. It wasn't one of the top two or three he always seemed to face, like the veela was. With everything that had just been on his mind a moment ago, though, and with the way he'd instinctively moved into a protective position as though it were Noble behind him instead of a man who was almost entirely a stranger, was it any wonder the boggart had seized on it?
It was different now than it had been in the past, both in the way to manifested (specifically the method of Noble's death) and in the feelings it evoked. There was the same lurch in his stomach as the last time he'd seen something like this, and that immediate, desperate thought:
I'm alone, and I can't do this alone, but now there was more.
I'm alone and it's my fault. I'm alone because I couldn't handle this on my own, and I gave too much of it to him. He's gone, and it's my fault. And yes, there was the sense of fear, but it was a distant second to the anger Ford felt grip him — at Noble, at himself, at the world.
"
Riddikulus," he cast, with more vehemence in his tone than was necessary. He was no longer having fun with this boggart, and he wanted it banished already.
The boggart Noble blinked, grinned at him, and wiped the foam away with the back of his hand. This was what Ford had pushed when he cast because it was what had worked before, when he'd seen Noble's death represented by boggarts. This death wasn't real, it was a practical joke, and it didn't mean Ford was alone, because now they were both in on the joke and they were both on the same team. This had worked before, but now when Noble laughed it only made things worse. The sinking feeling in Ford's stomach worsened, and the burn of anger in his chest intensified. Noble had laughed after the dinner party, too, before they'd fought about it.
"
Riddikulus," he said again, pushing the boggart towards something else. Noble's features melted into someone else's — the Muggle street magician Ford had seen in London recently. The magician did a trick, making a flower appear from his glove as though he'd pulled it from thin air. This was far enough removed that Ford was able to manage a laugh, though it was a little hollow. It was enough for an already weakened boggart, though, and it staggered backwards.
This was a critical moment in the process, and Ford moved quickly. He waved his wand at the first thing he saw that could serve as a container — what appeared to be an abandoned jewelry box — and positioned it behind the boggart, ready to catch it when it staggered back again. Boggarts resized to fit the space they had, being noncorporeal. It shrank into the box, eager for the reprieve from their constant assault of spells and laughter. When it had folded itself into the box, Ford surged forward to close the lid and murmured a sealing spell.
"So that's it," he said, turning to face Macnair with the jewelry box in his hands, as though it had been nothing.

Set by Lady!