The Starflash Opal

Zophenas is an enchantress but is trapped in the Underearth. How can she escape? She has heard of three possible ways; to find the soul of Waldo the warlock, to secure the magic ointment made by a witch, enabling her to fly and to capture a woman who has turned into a two-tailed cat.
For these tasks she recruits two schoolchildren - Swot, with a gift for maths and his sister Gemma. They find Waldo, who recalls hiding his soul in a bird. But which one? They retrieve it but the ointment - guarded by giant toads - is still needed. Zophenas helps by turning the children briefly into black beetles. The ointment is secured and unbaptised babies, used to bind it - and now also black beetles - rescued from the home of Hagatha the witch. Swot and Gemma also capture the woman who turns into a two-tailed cat. But when Zophenas is freed and the children are offered the starflash opal and the wishes, they make a surprising and wise decision.