Luckily there's two voices on the other side of the door, quiet conversation, and when Hanna knocks there's movement on the other side of the frosted glass in short order with Arthur's voice.

"Just a moment-" the lanky silhouette approaches, and when the door opens Arthur's face - the polite, neutral sort of friendly - breaks into a genuine smile at the sight of Hanna. "Hanna, hey! Come in, please." And he steps back to let him in.