Hearing a voice on the other side of the door, a voice that sounded like Lily's, Percy decided there would be no harm in opening the door and showing himself in. He sensed, from the experience of being raised by Molly Weasley, that she probably had her hands full.
"Yes, it's me. Where, um, are you?" Percy looked around, but not in a nosy or prying sort of way, as he stepped in.