[The reveal that Derek had actually gone home is actually a little shocking, and Isaac doesn't initially know what to do with it. His brow furrows a little and he takes a sip of his coffee to hide his expression, not entirely sure what Derek means.

Well... he knows what he means. He knows what he did. Parts of it, anyway, and Isaac feels like that's enough, isn't it?]

...I know. [Quietly. He repositions his hands on the mug and swallows hard, his eyes averted.] The other me- future me, or whatever... he told me. About being thrown on the streets. Replaced by your sister, or whatever.

[Isaac remembers the intense negative reaction that his other self had upon meeting with Derek, remembers the cornering, the explanation- remembers how the idea that Derek had thrown him out like that, violently and without explanation had colored his reaction toward him, even when he tried not to let it. Scott said it hadn't happened yet, he didn't know the details, he shouldn't punish Derek for something that he hasn't done, and Isaac had tried...

But now that it's out in the open, now that Derek knows he's done it, maybe there's something to be said for a resolution.]

I didn't want to tell you. I tried not to act any differently. But I- I know.