In the Green Isles, the summer magic is waning. Snake ships pillage the coastal towns, and the evil Icelord encases the verdant lands in a permanent frost. A mysterious old wizard prepares to mount one last defense of the Isles, hurrying to instruct his inexperienced apprentice in the art of shape-changing. In a desperate race to awaken the Summerlord, the newfound mage gathers a few remaining allies, including a seemingly ordinary young woman and her protective adoptive family. Mercilessly pursued by the Icelord's army of stormkin, they flee north to the seat of the Summerlord's power.

But the revelation of a family betrayal leads to new treachery?and time is running short for the Summerborn.