In Thaw, the twin diminutive "bird-rider" warriors Rist and Rusk ventured southward from their primitive, mist-bound homeland at the foot of receding glaciers, to warmer and more civilized lands downriver, where they experienced rewards, recognition, and resentment. But now, because of their notable achievements, the youngsters bear their new "man-names" -- Thist and Thusk. Holding important positions in the Sisterdom of ShadowFall, the twins find themselves defending the Princess of ShadowFall against an invasion from the army of a new Mother and her treacherous chief priest, at great cost to themselves and others. On the Moon, a strange child named Mien falls into a void being melted by the tunneling engineers of the underground Community. Through ancient technology once used solely by the Mother of Motherland, Thist on Earth makes contact with Mien on the Moon, a profound meeting that affects ShadowFall's very survival. The future is not always a peaceful place, as human desires and ambitions collide.