Stephen sat calmly there and listened to Matthew speak. And all this time, he hadn't known...of course he hadn't, he didn't want to. He'd wanted to believe Matthew was just one of the foot-soldiers, someone you probably could forgive for just being foolish, but Jesus. Of all the things he'd learned about Matthew over the past month or so...that really took the cake, didn't it?
"No," he breathed. That was one of the things you did have to realize, and something he'd realized a bit too late in life - no matter how much you liked someone, there were certain things you had to deem grounds for abandoning them. Mass-murder was one of those things. Or at least, Stephen knew this objectively, and knew his best bet right now, or at least, the one that would probably be fair, would be to go.
It didn't help, however, that he now had a full picture of how broken down Matthew really was. But still, he took in a breath through his teeth and said, "You're right. You've done absolutely unconscionable acts. I hope you get your due." He then pulled out a cigarette from the box in his pocket and lit it with his wand. "Hope you don't mind, but this is all a little much for me."
And so he sat there in silence for a while, staring straight at Matthew and smoking. He was panicking inwardly but unsure of how to make it look like he was just being menacing. On the one hand, he should have gotten up and gone, or at least hexed Matthew. Or something. On the other, in Matthew's current state, Stephen...didn't really want to leave him alone. It was a little bit possessive, but you couldn't say Stephen didn't have his own sort of weird, somewhat immoral idealism.
It came to him suddenly, like a flash of light. He tossed the end in his wine glass and smiled. "You know what I'm going to do, then? Seeing as you're in You-Know-Who's Inner Circle, I'd venture to say you know some things, and you're pretty valuable. So you know what I think?" He took his wand out of his pocket and pointed it at Matthew. "I think you're coming with me."