Challenge: Dumbledore's Army
Word Count: 100
Severus waited until later that night before activating the spell-solution he'd smeared on Weasley's robes. To his surprise, the magic led him to the wall opposite the tapestry of Barnabas the Barmy, and it wasn't until he remembered that there was a room behind it that he realized the dunderhead hadn't somehow managed to apparate within the school walls.
How to get behind it? What was going on? Severus walked the corridor once, twice, three times as he wondered....
And part of the wall became transparent to reveal a dozen children summoning their Patroni as Harry Potter corrected their wandwork.