After the death of their parents, the three young Fox children are sent to live with their uncle Herodotus at Coalthorn Castle. After the discovery of the Crescent Moonstone, their lives take a dramatic turn. They are forced to leave the castle to escape their uncle's clutches. Toby, Charity and Verity then set out to destroy the moonstone once and for all, although an unexpected visitor will change their plans.
Will the stone be finally destroyed? Or will their uncle Herodotus finally gain immortality?