Notes:

The Bean-Nighe , pronounced ben-nee'yeh, or Washerwoman at the Ford, is a faery related to the Irish Bean Sidhe (Ben-See, a.ka. Banshee).

The Bean-Nighe acts as a sort of cross between the Irish Banshee, as it washes the blood-stained clothes of those who are about to die whilst wailing mournfully, and the modern interpretation of a Djinn (Genie), in that it will grant you three wishes if you are able to sneak up on it and catch it.

Now because it's a Faery, and therefore a d---, catching it is also the only way to find out who is also actually going to die; which is kind of important considering everyone in a community wears similar clothes for day-to-day activities.