Hicks became the Vikings' first dragon trainer and successfully fulfilled his duty to ensure peace between dragons and humans. The peace they gained with their dragon Toothless loses its importance with Toothless's new discovery. Toothless discovers a dragon belonging to his own lineage, which he thought was extinct. This female dragon is fierce and fierce. When danger looms once again and Hicks' authority is tested, dragon and rider must make important decisions to protect their kind...