Former Livermore schoolteacher Patricia Boyle has written a young adult fantasy, “Traitor in the Realm,” about a teenage artist and her foster brother who become trapped in a magical world where they must balance a desire to return home against rescuing a medieval kingdom from a royal traitor.

The novel was released last month by Russian Hill Press in Livermore.

Boyle, who taught math and science for almost 20 years before retiring in 2015, said the story centers around teens from vastly different backgrounds.

Earth teens Kallan MacKinnon and her foster brother, Matthew Webbe, meet twins their own age in the new world,” Boyle said. “The four of them contribute unique skills as they cooperate to overcome life-threatening challenges.”

The cover art, illustrations, and maps in the book are the work of Livermore artist Susan Marchand.

The book is available through online outlets and bookstores.