Eleven-year-old Ezra Ben Castle of 23 Somerset Drive isn't your regular type of hero. He has a super-fast brain, a miniature schnauzer called Parker for a best friend, and a lingering sense that he's always been a little bit...elsewhere.

Primary school is almost over, but when the last day of term arrives, Ezra's granny is taken ill. With his adoptive parents preoccupied, non-stop rain soaking the garden, and the looming torture of secondary school to come, the summer holidays are definitely not looking good.

Meanwhile, in the distant world of Ankh Bah, the mysterious and powerful Great Bin Jah Meen has appeared out of nowhere, stopping the sun in the sky and using his dark magic to cast all who live there into the depths of anger and despair. Desperate for help, the Sahs—Ankh Bah's small, furry residents—end up somewhere unexpected.

When a half-sized steam train bursts out of a spinning portal at the bottom of Ezra's garden and two Sahs hop out, his dreary summer suddenly looks much more interesting, even if peril awaits...