In a conversation between lead character Detective Cormoran Strike and the victim's friend Hazel, the latter references the fact that her friend Kelsey was dating a boy named Niall.

When Detective Strike looks confused at the name, Hazel goes on to explain that is the name of Kelsey's favorite One Direction member. 'They're a band that came third on The X Factor. She's obsessed-she was obsessed-and Niall was her favorite," Hazel tells the detective through her tears.