Cillian is a fifteen-year-old boy who lives with his protective mother, Gillian. During the summer, he works in the nearby peatlands, where he harvests turf from the bogs. One day, Cillian is startled to see a human hand sticking out of the mud, and, when he digs around the area, he finds the intact body of a prehistoric girl preserved in the mud. Cillian is immediately infatuated with her, despite the long noose that is still around her neck from when she had been murdered hundreds of centuries before. Cillian falls in love with her immediately, and brings her home to live with him and his mother. Gillian is disturbed by the bog girl and her hold on Cillian, and her friends tell her that she should put the girl back in the bog before her son becomes lost in his obsession. However, Gillian suspects that if the bog girl leaves, Cillian will leave as well, so she allows the bog girl to stay in the house with some new rules in place. Soon, Cillian and the bog girl become inseparable, and other girls at school are visibly jealous of their seemingly-perfect relationship. The bog girl is adopted into a clique of popular girls, and she and Cillian even go to prom together. One night, Gillian and Cillian get into a fight about their opposing views on the bog girl, and Cillian accuses Gillian of not wanting to accept that he is growing up. She begs him not to settle for the bog girl, but he refuses to give up his love for her. Cillian thinks about how desperately he wants to get out of his situation and run away with the bog girl to live somewhere else. For months she has been a calming, silent presence in his life, never speaking or making any movements on her own, and she holds a constantly neutral demeanor. One night while Cillian sleeps, the bog girl moves on her own. She wakes Cillian up, and, for the first time, he is terrified of her. He screams for his mother to help him, and runs when the bog girl touches him. When Gillian comes upstairs, she tells Cillian that he has to make sure the bog girl gets home safely. Still in a state of shock and fear, Cillian takes the bog girl back to the bog and watches her sink into the water and disintegrate. He returns home to Gillian, still wondering who the bog girl really was.