It hadn't exactly been on William's itinerary for the evening, but Brendon looked excited about it, and William didn't want to disappoint him. Besides which, Brendon could probably use reinforcements, considering that he now looked younger than the typical sixth-year.
"Now I know why Pete struts around looking vigilant all the time," William commented, stepping back out of the doorway to let Brendon lead the way. "He probably collects enough partially-filled bottles from his students to last through the school year and then some."