Ivy lives in New Eden, a walled utopia where every citizen receives a daily dose of happiness from the Council. She works as a Feelings Monitor, watching for sadness in others, until one morning a handsome stranger named Adrian drops a small metal box into her bag and whispers a warning that shatters everything she believes. The box contains proof that the happiness doses are slowly killing people and that the Council has been harvesting the population for decades.
When Ivy begins to secretly test the doses, she discovers she is immune to them, which makes her the most valuable and most hunted person in the city. Adrian is a rebel from the dead zone outside the walls, and together they must expose the truth while fighting a forbidden attraction that grows hotter every night. The Council, led by the ruthless Cassian, will do anything to keep the city happy and obedient, including erasing memories and executing traitors.
As Ivy's sister Mira falls ill from the doses, Ivy's personal mission becomes a war for survival. She builds a network of rebels inside the walls, uncovers the horrifying truth about her own immunity, and learns that Adrian has been hiding a secret that could destroy their love. With the city's annual Happiness Festival approaching, Ivy must choose between saving her sister and saving the entire city from a fate worse than death.
In a final confrontation inside the Council tower, Ivy and Adrian risk everything to broadcast the truth to every citizen. The ending is hard-won but hopeful: the walls come down, the doses stop, and the people of New Eden must learn to feel real pain and real joy again. Ivy and Adrian walk out of the ruined tower together, free at last, with a new world waiting ahead of them.
