Earth has been a desert for 300 years. Eldritch creatures known as seraphim now roam the planet's surface at its new masters, consuming any form of life in their wake. Any human survivors were driven underground long ago, into subterranean colonies where they have stayed for centuries. The Boston colony had recently been wiped out due to a seraphim breach. Hannah Derryberry, chief engineer of the Rockport, Massachusetts colony, built a robotic horse for her husband, Daniel, and sent him out on a secret expedition in search of other colonies across America that may still be thriving. Left behind, Hannah contends with mentoring a Bostonian refugee, motherhood, and the degradation of the Rockport colony, knowing that Daniel's failure to find another sanctuary could mean the death of perhaps the last colony left on Earth and the end of mankind. The Horse That Hannah Built is a story with peril, uncertainty, and human connection.