In 1990, three boys are born, unrelated but intertwined by circumstance: Dayo, Iseul, and Youssef.

They are adopted as infants and live in a shared bedroom perched atop a mosque in one of Staten Island's most diverse and precarious neighborhoods, Coolidge. The three boys are a conspicuous trio: Dayo is of Nigerian origin, Iseul is Korean, and Youssef indeterminately Middle Eastern, but they are so close as to be almost inseparable. Nevertheless, Youssef is keeping a secret from his brothers: he has an imaginary double, a familiar who seems absolutely real, a shapeshifting creature he calls Brother. Brother is both a balm for the young boy and a curse-he provides solace to Youssef but demands information in exchange.

The boys' adoptive father, Imam Salim, is popular in the community, known for his radical sermons extolling the virtues of opting out of Western ideologies. But he is uncharismatic at home, a distant father who spends evenings in his study with whiskey-laced coffee, writing letters to his former compatriots back in Saudi Arabia. Like Youssef, he too has secrets, including the cause of his failing health, the reason for his nighttime excursions from the house, and the truth about what happened to the boys' parents. When Imam Salim's path takes him back to Saudi Arabia, the boys will be forced to follow.

There they will be captivated by an opulent, almost futuristic world, a linear city that seems to offer a more sustainable modernity than that of the West, and will find traces of their parents' stories. But they will have to change if they want to survive in this new world, and the arrival of a creature as powerful as Brother will not go unnoticed.