The four-part Netflix series “Adolescence” got off to a strong start after it was released March 14, and fans have been quick to note the show’s many ups, downs, and emotional moments. But there’s one small — but devastating — hit that might be easy to overlook.

The series concludes with a version of the song “Through the Eyes of a Child.” Though the original is sung by Aurora, the version in the show is sung by Emilia Holliday, who plays the young girl who is killed.

Director Philip Barantini made the reveal in an interview with Netflix.

“The voice in the score is Katie’s voice,” he explained. He added that once the team learned Holliday could sing, they made the decision to include her version of the song. “Katie is a part of the whole series,” he added. “Her presence is always there.”

The story of a young boy (played by Owen Cooper) who is accused of killing his female classmate is difficult to watch. It becomes clear early on that Cooper is guilty of the crime, which means the rest of the series explores the gut-wrenching process through which the truth is uncovered, as well as the journey the parents of both children are forced to take.

“In the U.K., there’s a real problem with knife crime, certainly in the younger generation. There have been a series of of young boys who were killing young girls with knives, and it was really upsetting,” director Philip Barantini told TheWrap this month. “That was the seed that we wanted to explore, and send a bit of a message and maybe spark a bit of a conversation.”

Writer Jack Thorne also said he didn’t want to come up with a story that immediately blamed Jamie’s parents for his crime. “‘I don’t want to make this easy and blame the parents. I want to create a complicated portrait,” he explained. After a female colleague suggested he explore incel culture online, Thorne soon realized he had a starting point for Jamie’s radicalization.

The series also stars Stephen Graham, Owen Cooper, Erin Doherty, Ashley Walters, and Faye Marsay.