Thirteen-year-old Rowan Popplewell and his younger sister Nina are sent to spend the summer with their two eccentric great-aunts in Owatannauk, Maine, a town with 104 residents and as many secrets. Rowan wonders why there isn't any electricity, where his aunts get the priceless antiques that fill their "curio" shop, why the tiny town has a library to rival the world's best, if Aunt Agatha can really read his mind, where Aunt Gertrude disappears to at night, but most of all, what is going on every sunset, or "golden hour", at the old, abandoned resort hotel on the edge of town? The resort turns out to be an elaborate time machine, built by a mad genius who has long since disappeared. Cautious Rowan wants nothing to do with the place, despite the urgings of two adventurous new friends, twins Xanthe and Xavier. But when Nina disappears too, the kids have no choice but to follow her on a dash through time, straight into the terrors of the French Revolution.