While being persued by bullies, Eustace and Jill Pole are magically transported to Narnia where Aslan has an important task for them; to seek out and find the long lost son of the aged King Caspian.

Jill and Eustace are introduced to Puddleglum who agrees to be their guide to the ruined city of the giants, but will their new found Marshwiggle friend meet his fate before they manage to get there?

Journeying on, Eustace, Jill and Puddleglum meet a lady in green who gives them directions to the castle of Harfang with the promise of food and shelter. But will their eagerness to get there distract them from their mission and make them miss another of Aslan's signs?

After some angry prompting by Aslan, the group realise they need to get back to the ruins and follow the instructions 'UNDER ME'. But how do they get out of the castle? And do the giants have ulteria motives for being so hospitable to two human children and a Marshwiggle?

Jill, Eustace, Prince Rilian and their brave friend Puddleglum face a fight to the death with the Green Lady.