Out in the English countryside near Glastonbury, the legendary location of Avalon, three kids play at crusading for King Arthur as knights of the Round Table. When an American girl, arrives in the neighborhood, she's a bit of excitement in an otherwise boring summer. But things get even more thrilling when an enemy plane crashes nearby and the kids discover a mysterious stranger in the wreckage. Is he a German spy, a lunatic escaped from the local hospital, or might he just be who he claims to be - King Arthur, back from Avalon to save Britain?