In the land of Barracks, the economy thrives on the barter of their citizen's most precious commodity-a human heart. Each year the Heart Reign festival is thrown for those who have become of age to trade their heart for their deepest desires. And this year is Adelaide Tye's year to trade. After despising Heart Reign for years, Addie endures her Extraction and discovers that her heart isn't gray and dying, like all other hearts in Barracks, but bright red, alive, and teeming with power. With a warning from the extractor of hearts, Addie rushes through Heart Reign to make her choice-trade her heart to Schism, the monster who took her brother years before, or go in search of the Mender-a mythical man said to purify hearts and save her own heart. Either decision will rip her away from the one man who has always been by her side. Knowing there is only one real choice to make, Addie jumps through Schism's red door and is thrust into a dark and dangerous realm where she is faced with making a trade she may not survive.