Maisie and Jasper are left in New Hampshire with the peculiar Professor Winslop when their parents go to England for work. Winslop's lessons on mythology are terrible, but when the children discover a huge circle of stones and encounter shamans of the Dark Ones lurking in the woods, those myths are the only thing standing between the twins and the nightmares the Shamans hope to unleash on the world. Maisie and Jasper must assemble the mythical Crown of Seasons before the Winter Solstice if they are to have any chance of saving the world from the minions of the Dark Ones.