A psychiatrist, Martin Dysart, investigates the savage blinding of six horses with a metal spike in a stable in Hampshire. The atrocity was committed by an unassuming 17-year-old stable boy named Alan Strang, the only son of an opinionated but inwardly timid father and a genteel, religious mother. As Dysart exposes the truths behind the boy's demons, he finds himself face-to-face with his own.