Amid the Philippine-American War in 1901, a young teacher from Iowa, Eleanor Karsten, sails on the US Army Transport Thomas to America's new territory, the Philippine Islands. In response to President McKinley's call to help implement the policy of "benevolent assimilation of Filipinos," she joins more than 500 US educators (the "Thomasites") to teach Filipino children and build a secular public school system as an alternative to the Catholic educational institutions established by Spanish colonial rule.

A stopover in the Hawaiian Islands and a brief residency in Manila, where the Thomasites await deployment to their designated school areas, awaken Eleanor to disturbing implications of America's expansionist policy. She eagerly welcomes her assignment to Magayon, home to the majestic, perfectly cone-shaped Mayon Volcano. When she arrives there, however, various challenges-including malaria, a cholera epidemic, insurrection, and racial and religious prejudice-test her resolve to fulfill her mission.

Her loyalties are likewise tested when she unwittingly becomes romantically entangled with a Spanish-Filipino plantation owner and his peasant foreman. Worse, Eleanor worries one of them could be the local leader of the insurrection, thus setting her at odds with the commanding officer of the U.S. infantry stationed in town. Even worse, she clashes with the parish priest.

As Eleanor witnesses the ramifications of the U.S. occupation of the Philippine Islands, she finds herself the student rather than the teacher. Caught between, on the one hand, her compassion for her students and Filipinos and, on the other, her patriotic duty to her country; her devotion to her vocation and her increasingly undeniable feelings for one of the men competing for her love; and the scorching battle between ideology and reality-Eleanor struggles to balance treading on a tightrope of volatile, interwoven interests and carve a path forward.

Would Eleanor survive the forces tearing her and her mission apart, including the people she's come to love as her own? To whom would she finally entrust her heart? And what legacy would she and her fellow Thomasites leave for generations of Filipinos?