Wyrd Sisters by Terry Pratchett

Up in the Ramptop Mountains of Discworld three witches have come together to form a coven. Granny Weatherwax, as the most highly regarded witch in all of the Ramptops, is the unofficial leader. She doesn't approve much of these newfangled ideas youngsters have now a days, but of course, she doesn't approve of much period. Nanny Ogg skipped over the tradition of a witch living a lonely life in a remote cottage, and instead is the matriarch of a large clan that seems to have spread to every corner of Lancre. Magrat is the youngest of the three, and the one with the most newfangled ideas. She sees a place for great ceremony and ornamentation whereas the others just want to get things done. Despite their differences, however, each witch has power.

These "Wyrd Sisters" might have continued living their witchy days in relative peace (as peaceful as life gets when people are always hounding you for this cure or that) if it wasn't for some political intrigue they managed to get themselves caught up in. A duke has killed the King of Lancre, and some of the loyal guards whisk away the royal babe to prevent him from meeting the same fate. When the last loyal soldier is dead (and those not loyal have been frightened out of their wits), the witches find themselves in possession of a baby boy.

Now as a general rule witches do not meddle in the great affairs of the world, but even Granny Weatherwax can't deny the need to protect this baby boy. So, in their own bumbling way, the witches find a way to safeguard him and his crown. They leave him the last place anyone would look, with a troop of traveling players, and hide the crown in amongst all the prop crowns.

This might have been enough, but the very land of Lancre eventually begins to cry out against the evil Duke, and the witches find themselves sorely tempted to meddle just a little bit more...