Caterwauling Charm

From UnknowableWiki

The Caterwauling Charm is a spell that sets in place an extremely loud alarm. On Voldemort's orders, there is a Caterwauling Charm in place in Hogsmeade by May, 1998, as well as a strict curfew and anti-Disapparition measures (DH28, DH29). The alarm is set off by the presence of anyone in the streets of the village after hours.

The Trio sets off the alarm when they Apparate to Hogsmeade in order to search for the diadem of Ravenclaw. A dozen Death Eaters leave the Three Broomsticks as soon as the alarm sounds; they suspect that Harry Potter has come to the village. Dementors approach the Trio, and Harry casts a Patronus Charm to ward them off. Aberforth Dumbledore quickly intervenes; he orders the three teenagers to hide in the Hog's Head, and claims responsibility for putting his cat out, and thus setting off the Caterwauling Charm. Aberforth also states that the Patronus is his—a goat, not a stag (DH28).

In order to avoid setting off the alarm, Neville Longbottom and other Hogwartians arrange it so that supporters of the castle Apparate directly into the Hog's Head (DH29).