After a summer camp gone wrong beneath the Scottish Highlands, fourteen-year-old clarinetist Anna and her eleven-year-old engineer brother Elliot are sure their secret pact with the brownies of Lumathir is safely buried underground—along with the ash salt, the runic flute, and the ancient Old Oak that guards the magic between worlds. But time runs differently below the roots. While only weeks have passed in their English red-brick neighborhood, three years have gone by in the tunnels, and a vengeful brownie saboteur named Hamish has escaped his prison, carrying a new war straight into the foundations of their home.
When clocks freeze at 10:15 p.m., roots split open under the hallway closet, and a friend from Lumathir collapses at their feet, Anna and Elliot are dragged back into a battle where music and engineering are the only weapons that matter. Guided by a living amber gem, a petrified-wood flute, and a copper gauntlet of Elliot’s own invention,
