Wyrd Sisters: Terry Pratchett

Three witches - Granny Weatherwax, Nanny Ogg and Magrat Garlick - have gathered on a lonely heath. A king has been cruelly murdered, his throne usurped by his ambitious cousin. An infant heir and the crown of the kingdom, both missing . . .
Witches don't have these kind of dynastic problems themselves - in fact, they don't have leaders.
Granny Weatherwax was the most highly-regarded of the leaders the witches don't have. But even she found that meddling in royal politics was a lot more complicated than certain playwrights would have you believe . . .