Eleven-year-old John Egan knows he has a special gift: he can tell when people are lying. Their untruths set his eyes stinging and his stomach heaving. John thinks that one day his gift will make him famous and guarantee entry into the the Guinness Book of World Records. Until then, he has to navigate his father's anger and his mother's abrupt and confusing changes between treating him like a little boy and a then like a man. When the family is forced from their rural cottage into the council-flat slums of Dublin, John discovers that the lies that make him sick are also shielding him from the truth that threatens to destroy his family.