Guy Green's social drama stars Stuart Whitman as the title character, a man whose unhealthy childhood has left him bewildered by sex. After an affair with a woman his own age ends badly, Mark finds himself increasingly drawn to young girls, who he feels do not pose the same threat of emasculation that adult women do. When he is charged with kidnapping a ten-year-old girl in order to molest her, his conviction results in a three-year prison sentence. With the help of Dr. Edmund McNally (Rod Steiger), a prison psychiatrist, Mark comes to terms with his urges and is released from prison a changed man. Soon after, he gets engaged to Ruth Leighton (Maria Schell), a widow with a ten-year-old daughter of her own. After Mark is seen in the vicinity of a recent molestation incident, a journalist digs into his background and his past is brought to light, destroying not only his relationship with Ruth but his fledgling career as well.