Johnny Littlehorn is on his way to France to live with his Uncle Paul. But what starts off as an exciting trip soon turns into a frightening adventure. A strange man trails Johnny throughout Paris, and seems to follow him to his Uncle's home in the small St.Charmant. And then, as Johnny explores the town with his new friends, he realizes something even worse: a Nazi spy hiding in the mountains, hatching an evil plan. Could the two men be one and the same? And can Johnny foil the villainous plot?