How did your Shep handle Horizon?
Unintentionally, as a death sentence.
In the moment itself, there's a lot of very quickly fluctuating emotions. Relief that he wasn't too late, that Kaidan's alive. Unease in not recognising Kaidan because his anger is so unfamiliar. A sickly deep dread when Kaidan mentions they were tipped off on Horizon--he was used as bait, Emrys knows he was. Protective resolve in pulling back, letting Kaidan go free from being dragged into this mess.
But what burns the most is the guilt of being selfish enough to convince Kaidan to love him, the guilt of etching pain so deeply into the man that he feels unfamiliar now. And for what? A few weeks together? Emrys caused him years of pain, for a relationship that formally spanned a little over a month. And he knew, he knew that death is always right around the corner for them. What if they rekindle, only for Shepard to die again? It would be worse, this time, Kaidan left not knowing if Shepard was truly dead or if he would pop up again some years later--grief haunted by the perpetual knowledge that there's no longer any certainty, that gone doesn't always mean gone with Shepard now. But what if he is gone, and Kaidan wastes a life waiting for a man to come back who never does?
Besides, he's surrounded by people who are tying up their own loose ends and preparing for a suicide mission, who is he to be any different? He's trapped living on the cusp of his worst nightmare, feeling more and more parts of himself break each day. He's long since stopped feeling like a person, he knows he's just a tool and people like him aren't made to have love--he's made to do a job and be done with it. Maybe that's okay, maybe that's just how it is, maybe he was a fool for letting himself think otherwise.
But of course, he doesn't die--he's, if nothing else, a damn good tool. It's takes a long time of a quiet detention and a lot of psychiatrists for him to start processing the place he ended up, but he reunites with Kaidan on much shakier feet. He doesn't really tell Kaidan what happened, not all at once, but Kaidan can tell enough by the way Emrys holds himself like a kicked dog when it's late and they're alone--like he isn't sure he deserves this any more.
Kaidan worries that it's his fault, that what he said on Horizon, on Mars, was too much, but it wasn't. Emrys never blames Kaidan for that; he's very open about the fact that if Kaidan did come with him, he doesn't know if he would've been able to trust him. He needed someone to see that what was happening was wrong, beyond just the ethics. He needed Kaidan, who knew Emrys, who could see him, to be horrified at what he saw of him that day, to know that something must be so deeply, deeply wrong that he has to turn and leave immediately because that isn't his Shepard, not any more, not right now.
