Brendan's initial marvelous adventure began when he met the great wizard Patrick, who taught him to "float on the wind." The pair then traveled to Magnifica, the fairy capital, where they met Queen Sharon and the fairy community. Their adventures in Magnifica even included heroically saving twenty fairies from attacking hobgoblins. Brendan and Patrick then returned to his home in Ballybunion.

Queen Sharon had pleaded with Brendan to become her "knight errant," and Brendan eagerly agreed. No sooner had he consented to the queen's request than she informed him of a dire situation that she believed he could resolve. A community of nature nymphs in the forest of Roscommon County was being terrorized by a "Pooka," a changeling that had taken the form of a gigantic fire-breathing horse.

Brendan accepted the challenge, and the grateful queen instructed him on how to ride the Roscommon Rainbow to the secret nymph village. A frightful and rewarding adventure awaited him with the Pooka and the nymphs.