Arthur Hallet, a young English boy, finds himself in difficulty at home, through certain harmless school escapades, and enlists in the famous "British Legion," which was then embarking for Spain to take part in the campaign to repress the Carlist uprising of 1836. Arthur shows his mettle in the first fight, distinguishes himself by daring work in carrying an important dispatch to Madrid, makes a dashing and thrilling rescue of the sister of his patron, and is rapidly promoted to the rank of captain. In following the adventures of the hero the reader obtains, as is usual with Mr. Henty's stories, a most accurate and interesting history of a picturesque campaign.