Yeah, that's basically what I remember about this story. I think it was long, although I don't remember if by long I mean 10k or 50k or more or less or what. I'm relatively new to The Sentinel both as a show and as a fandom, so I know it was out there recently, but I don't remember what website I read it on. I mostly read on AO3, but for a while I was looking at other sites, and I don't know which ones they were.
So, here's as much as I can remember. Blair is in love with Jim. He doesn't say so, of course. Jim starts having feelings for Blair, but doesn't believe that he can really be feeling like that. I remember him saying that he couldn't love Blair, couldn't want Blair, so what was left, and eventually decided that he needed Blair. At some point fairly early in the story, something causes Jim to run away from the Loft, and he goes out into the woods, where he sees the spirit version of himself that the Jaguar sometimes turns into. It says that it's leaving him, because it is going down a road with regard to Blair that Jim's refusing to follow. Jim feels like there's nothing left. He zones. Blair finds him in the forest eventually, after getting worried about how long Jim was gone. He finds him, brings him out of the zone, and brings him home. For some reason they're in the shower together, and Jim starts kissing Blair. He's not really aware of much aside from that he needs Blair. He does notice the taste of salt on Blair's lips as he's kissing him. I don't remember how far they go, if they had full-on sex, or whatever, but Jim keeps telling Blair that he needs him. Afterwards, Jim sort of comes back to himself, and realizes that the taste of salt on Blair's lips was from tears, and that Blair was crying. He's afraid he might have forced Blair to be with him. I think they have some conversation in which Jim tells Blair that he won't touch him again, which might have happened after Jim sees Blair flinching from his touch, or possibly after Blair seems uncertain about going to his own room at night or upstairs with Jim. Time passes. At some point, Jim asks if Blair will let him hold him while they sleep, while promising not to touch him any other way. Something happens to put Blair in the hospital, I don't remember what. Jim's there when he wakes up, of course. They both see the spirit version of Jim in the doorway, beconning to Blair to come with him. Jim is terrified that Blair will leave him, after seeing the look of longing on Blair's face, saying again that he needs Blair. Blair says that he knows, and that he won't leave, it's just that the spirit Jim loves him. I think Blair is crying again at this point. Jim takes this opportunity to finally get a clue and realize that he loves Blair, which he then tells him, so they ultimately end up together.
Okay, I remembered more detail than I realized. I still can not for the life of me find this story. So if you know the title or the author or a website where I can find it or something, PLEASE help me, before I go insane.