When Liam walked in without Nick, Kelly knew already. He knew before anyone asked, he knew possibly before anyone else thought it. He knew from the look on Liam's face. It was the same look that Liam had had in service when he spoke about a fallen comrade, it was the same look he had when he recounted a mission that had been FUBAR. It was probably the same look any of them gave their brothers when they had to recount such issues. So, Kelly knew.
He vaguely heard himself saying "no" anyway, he heard himself saying the negative even as he was begging the universe for this to be a lie, for Liam to be wrong. Liam was never wrong though, and despite the fact that he had got Nick working with him by nefarious means, that didn't mean that it wasn't obvious Liam cared for Nick. They'd been close in service, and working together they were becoming close again. Kelly knew that Nick had been playing up some of it, getting Liam to trust him again, to talk to him again, but Kelly also knew Nick. He knew how he worked and also how good a judge of character he was. Nick could hide his feelings from a good many people, Kelly would wager it was only Ty that Nick was also unable to hide from, but Nick couldn't hide his feelings from him.
Liam had been alone so long, and he finally felt like he had the chance for that to change, the chance to have a friend for the first time in years, and he'd failed him. He'd finished the mission he had been sent on, but at what cost? An honourable and good man had almost certainly died and he, a man who had long ago traded his halo in, if he had ever had one, for a pitchfork was still alive. It wasn't fair. The universe had a fucked up sense of righteousness.
Kelly had felt all the breath leave him somehow all at once when Liam had intoned that he had seen Nick been carried out and that he "wasn't fighting". And then suddenly everything that Liam had ever told them, every lie they worried had been just that, came flooding back into his head all at once and he heard himself rail against the injustice of it all, rail at Liam as the arbiter of all of the current stress, the current worry, the current way his heart was breaking.
When Ty said he'd join him in searching for Nick, Kelly felt himself slump in relief. He hadn't realised quite how tense his muscles were, how close around his ears his shoulders had become. Hearing Ty saying they'd go after the love of his life, was music to his ears, he couldn't even give himself time to worry about what that could mean for Ty and Zane themselves, about how going after Nick could mean they wouldn't be able to fix their own lives. Zane saying that it was no good sacrificing their friends to save themselves made Kelly want to cry, but he couldn't, not then. He had to be strong, for Nick.
He had to get him back, and they were all going to get him back, he had no doubt about that, because he couldn't imagine a world without Nick O'Flaherty in it, didn't want to imagine that world. It would be a world that was all the poorer for the light he gave off, even if he himself didn't believe he was a good man, Kelly knew different.
Nick was a pure soul, and Kelly abjectly refused to be part of a fantasy where he was dead.