Qui remonte l'horloge de la ville quand elle s'arrête ? Qui ramène les bateaux égarés au port ? Qui veille sur ceux qui se promènent en forêt ? "C'est le Géant !" assure GrandPa. Mais Billy ne le croit pas...

"He has hands the size of tables," Grandad said, "legs as long as drainpipes and feet as big as rowing boats. Do you know who I mean?" "Yes," sighed Billy. "The Secret Giant. But he's not real!" Billy doesn't believe his Grandad when he tells him there's a giant living in his town, doing good deeds for everyone. He knows that a giant is too big to keep himself hidden.

And why would he want to keep himself a secret? But as time goes on, Billy learns that some secrets are too BIG to stay secret for long...