“They landed in a huge circle of white dust, with a rim of sharp-looking rocks all the way round the outside. Everything was bathed in harsh colourless light, like moonlight but ten times as powerful. In the middle of the circle of rock was a massive square stone slab, and on the slab, flat on his back, lay a giant with his eyes closed.”
The children fly with some owls to the moon, where they meet the Queen of the Night and hear the story of Pandora and Prometheus. The seventh chapter of twelve.
(If you don't see links to all seven chapters when you get to the Puzzle Box index-page, click CTRL + Refresh to update the page.)