Adrian was surprised by a knock on the door but knew of only one person it could be - his family would've come in via floo, and he doubted anyone besides they and Alicia (and the twins, of course) even knew this was his flat, let alone would come and visit it. And so he took a bit of time while he wiped his hands clean of the crushed root he'd spent the morning testing and experimenting with, and then headed to the door.
Out of his potions lab (the spare room in his flat) and through the entertaining room (not that he ever did any, but there was a magicked muggle tv and dvd player in there), he opened the front door with a bit of a smirk. "You know some of us work during the day," he barely looked at her before turning and moving back into the apartment, knowing she'd follow him in if she felt like it.
Grabbing two bottles of water out of the fridge he turned back to her and gave her a look as if to say what? while he handed a bottle over and settled onto a stool at the bar that separated his kitchen from the main room.