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 program doesn’t make mistakes, and by the end of the night, Zada is engaged to a man she doesn’t love. Desperate, Zada turns to a surprising ally: her daringly beautiful former best friend, Daphne. Despite their estrangement, Daphne may be the only person who can help Zada uncover the truth about Heartsong. But can she trust her after all this time? And if what they find upends everything, can Zada find the courage to choose what she believes—and who she loves?