Charles considers asking to be let in, but his hand has already found and started turning the door handle. He is feeling neither reasonable nor rational right now and, presumably, if Erik wants to be left alone, he'll have locked it or stuck the mechanism.

But it swings open, although rather than enter, Charles stands in the doorframe and looks at the man before him: slouched, silent, smaller seeming. Oh, Erik.

And he slumps against the doorframe, something immensely sad in his bearing. "You saw, didn't you." It's not a question.