
Adolescence's devastating ending revealed the main reason why Jamie Miller decided to kill one of his schoolmates, Katie Leonard.
The new limited four-part drama series from Netflix follows how a family deals with a 13-year-old boy's decision to take bullying matters into his own hands by doing the unthinkable to Katie Leonard.
Why Did Jamie Miller Do It in Adolescence Netflix?

Adolescence delivers shocking twists and turns involving Jamie Miller (portrayed by breakout star Owen Cooper) after he gets arrested right off the bat in the opening moments of Episode 1 for suspicion of murder.
As expected, his parents, Eddie and Manda Miller, believe that he is innocent, making viewers feel that Jamie is not capable of committing such a heinous act (the boy even peed his pants while being arrested).
However, as the series progresses, it is clear that something is not right with Jamie.
At the end of Episode 1, Detective Inspector Bascombe and Detective Sergeant Misha Frank pulled CCTV footage showing Jamie stabbing Katie seven times in a parking lot, ultimately confirming that he indeed killed her.
Anchored by stellar performances from Adolescence's star-studded cast, most of Episodes 2 and 3 revolve around exploring why Jamie did it, including the detectives deciding to interview students at Bruntwood Academy to learn more about Jamie and Katie.
Episode 2 unveils who supplied Jamie with the murder weapon while also shedding light on some Instagram comments that end up being crucial to the case.
In Episode 3, Jamie has a tense-filled final session with his clinical psychologist, Dr. Briony Ariston, where viewers find out why Jamie committed murder.
It turns out that Jamie killed Katie fro several reasons, mainly due to his lack of self-esteem, troublesome bullying at his school, and unpacking incel propaganda on Instagram.
These factors contribute to Jamie's insecurity. He was like a ticking time bomb waiting to explode, and Katie was the tragic victim.
After Katie accuses him of being an incel following her comments on his Instagram, Jamie takes it personally, which ultimately leads to the stabbing incident and Katie's tragic death.
In an interview with Radio Times, Adolescence star Christine Tremarco, who plays Jamie's mom Amanda, explained that the decision to include the topic of "incel" in the series is to "educate everyone" that this propaganda is happening in real life:
"It's to make people aware because even when I first read the scripts, I had no idea what an incel was. I had no idea that this was happening, and with kids as well. [We want] to educate everyone – parents, children, because it's happening with children."
What Happened to Jamie in Adolescence's Ending?
After the truth about Jamie was revealed in the first three episodes, Adolescence Episode 4 (the finale) focused on the ramifications of his actions toward his family.
The Miller family, led by the patriarch Eddie, is still reeling over what happened. While they believe that there is a light at the end of the tunnel for Jamie, one phone call changes the narrative's trajectory.
Jamie calls Eddie to let him know that he is changing his plea to guilty, indicating that he is ready to take accountability for his actions while fully admitting to what he did to Katie.
This is the final nail in the coffin for the Millers, and this revelation allows them to move forward even if it is heartbreaking for them to do so.
All episodes of Adolescence are streaming on Netflix.