The Elfstone (Paperback) (ISBN-13: 9781913892944)

Penry is the youngest son of the Dark Lord of the Svartalfar. He would like to be wicked and devious to earn the approval of his father, but he's not very good at it. His schemes keep getting him into deep trouble

Mackenzie is an African-American teenager attending Summer School in England while her mom is at a conference. England is boring, and a weird Goth kid has caught her interest. She's smart and capable, so she'd be more than a match for Penry if magic wasn't involved.

Morag and Boyd will need all of their new-found knowledge of the Otherworld if they are to save Mac from Penry, and Penry from himself. Especially as Penry's latest scheme involves the High Queen of the Fair Folk.