Fennymore and the Brumella

Eleven-year-old Fennymore lives alone in an old house with only a magical bike for company. After his great-aunt dies, Fennymore sets off with his new friend Fizzy to find his parents, who have disappeared. They fall foul of a silvery grey gentleman and an evil doctor who wants to get his hands on a mysterious invention, but Fennymore finds a maybe-dad. And a brumella. Whatever that is.