Erik gives a thoughtful noise, but that's when his focus turns to something else entirely -- Charles' lips and the unearthly colour of them, the way they shape when given to distraction and how Erik finds himself utterly taken by them. In effect, it's what's put him back to something he vaguely remembers.

An old bedroom, held before the war, before the ghetto, where he might've taken a high school sweetheart had he ever attended.