In the utopian city of New Ionia, everyone gets a soulmate and Zada can t wait for hers. Now that she s eighteen, it s her turn to meet her destiny with the help of Heartsong, an algorithm that chooses your perfect match for you. Then Zada crashes into her soulmate, setting off their shared Heartsong, and the unthinkable happens: she feels nothing for him. But the Heartsong program doesn t make mistakes, and by the end of the night, Zada is engaged to a man she doesn t love. Desperate for a way out, Zada turns to her beautiful, reckless, and utterly impossible former best friend Daphne. Together, the two embark on a quest for the truth that throws Heartsong and their entire world into question. As time runs out, Zada must find the courage to choose what she believes and who she loves.