¡°This is a useful little spell,¡± he told the class over his shoulder. ¡°Please watch closely.¡±
¡°Ready?¡± said Lupin, gripping the box lid.
Fred pulled something from inside his cloak with a flourish and laid it on one of the desks. It was a large, square, very worn piece of parchment with nothing written on it. Harry, suspecting one of Fred and George's jokes, stared at it.