In 1980 Colorado, Aletha Kingman comes to the ski resort of Telluride to find refuge from a shadowed life. Cree Mackelwain comes to find the secret of his dead partner's involvement in the drug trade. In 1901 Colorado, young Callie O'Connell faces a destiny of poverty and shame on the forbidden side of town. Her brother Bram faces a lifetime of danger in the gold mines along with the gathering threat of bloodshed between miners and their bosses. At the Threshold, they meet Aletha and Cree, astonished time travelers from a modern era. Now Callie and Bram must confront not only the unbearable struggles of their own world but the unimaginable doorway to the future...