The Tale of the Dragonstone

The Parker children; Lucy (12), Millie (14) and Tom (15) live with their parents in a small village at the lower end of a quiet, wooded valley.
Lucy is very ill and needs an operation that can only be performed in America.
While out in the woods one day Millie is taken to a dragon's lair where the dragon tells her that it knows of Millie's love for her sister and that it will cure Lucy. This it does.
The next year, in the early spring, the youngsters are asked by the friendly dragon to help get it's dragonstone back. ( A dragonstone is the centre of a dragons magical powers.) The young Parkers go to the strange world of Eldos and on their quest they meet elves, dwarves and many strange creatures.
They make quite a number of friends, and after many strange adventures and a battle on dragon back with an Inner Kingdom border patrol, they make their way back to this world and home, bringing with them the dragonstone.