In the intervening years, the inhabitants have lost their understanding of science and have regressed to a Medieval state of technology, aided by their use of voodoo, telepathy, and magic.
Change is set in motion when a maverick apprentice Jinxman starts to rediscover the scientific method and learn about science.
The first colonists were still worried about the risk of attack, so they built huge fortresses and mounted heavy weapons from the spaceships on the ramparts.
The planet is divided into feudal territories that are defended by mounted knights and foot soldiers carrying crossbows, swords and spears.
The telepathy is done by skilled “Jinxmen”, who cast spells and manipulate enemy troops using wooden cabinets filled with small voodoo dolls representing their opponents.
The structure not as pure as The Dragon Masters and theme not as developed as The Last Castle, The Miracle Workers nevertheless displays all of the imagination and cleverness that are Vance’s trademarks".