Greywater, beneath the Prism Spire, a year after the light at its crown went dim. One by one its colors have drained away, and apprentice lens-grinder Wren Hallow has watched her grandmother Oma Sel's eyes cloud with every grey evening. Now Oma asks for one real sunset while she can still see. So Wren will build a lantern around the sunset her grandfather once caught in a glass bead, and climb. A luminous, bittersweet adventure of glass and light.