Maddy has always been able to see things that other people can't, but she didn't know it might have something to do with the mother who died giving birth to her. Now her father has decided to move back to Scotland, and for the first time in her life, Maddy has a chance to learn about her mother's family and the strange circumstances surrounding her own birth.

Maddy was born on a fairy hill—the same hill that the the 17th century writer Robert Kirk wrote about in his book The Secret Common-Wealth, and just like Kirk, Maddy's mother may not have died there. Like Kirk, she may still be alive, living in the Otherworld, and Maddy may even be able to see her.

If Maddy can rescue her mother from the fairy hill, maybe her father won't be so sad all the time. But what if her mother doesn't want to be rescued? And who is the mysterious dark-haired boy who calls Maddy "milk sister?"

The Secret Common-Wealth is a middle grade/YA fantasy novel.