Netflix's hit show Adolescence ending explained – the real reason why Jamie killed Katie 

In episode one, Eddie and Manda's son Jamie is shockingly arrested for the murder of his classmate. After extensive police questioning, with Jamie denying that he had anything to do with Katie's death, they are eventually shown damning CCTV footage of Jamie killing her— with the show then shifting into the question of why Jamie did it rather than if he did it.

Episode two looks at modern-day school life, as two detectives on the case visit Jamie and Katie's school to request that anyone who might know anything come forward and share information.

They are eventually told that, while messages between Jamie and Katie appeared to be friendly, the emojis actually suggested that Katie was mocking Jamie for being an incel—meaning involuntary celibate, which is connected to the rise of misogynistic culture, particularly among young men.

Actor Ashley Walters spoke about the influence of 'manosphere' influencer Andrew Tate, explaining: "I'd seen bits of the Andrew Tate stuff kind of popping up online or whatever, but I never really delved into it. And for me, this was the first real experience.

"I do sometimes feel sorry for [kids]. When I was growing up, I was in a bubble. I didn't have a clue what was going on in the States and other parts of the world. It was just kind of in my little area that I grew up in with my family... I wasn't seeing Bentleys and designer clothes and all of this stuff. It's like I was happy with what I had. And now you're exposed to everything. It's no wonder that kids mentally grow up quicker."*

Episode three delves further into Jamie's mindset, as a psychiatrist sits with him and discusses his thoughts and feelings towards women, spurring him into a terrifying rage and shocking aggression towards the female psychiatrist. It is revealed that Jamie was rejected by Katie after asking her out when she was "weak," after topless photos of her were shared at the school. He describes himself as "ugly" and lies about his experience with women.

In the season finale, Jamie's father Eddie has the worst birthday as someone vandalizes his van, and Jamie calls to tell him that he is planning to change his plea to 'guilty,' finally confirming to his parents once and for all that he did kill Katie. This leads them to examine their missteps as parents as well as their shock at what Jamie was exposed to while they thought he was safe in his bedroom.

In the final moments of the episode, Eddie goes into Jamie's bedroom, which appears to be a sign of his total innocence—with posters on the wall, starry wallpaper, and a teddy on the bed. Sobbing and saying that he should have done better, he tucks Jamie's teddy into bed.

Speaking about the ending, Stephen told Radio Times: "We always knew that we'd end it in the room, that was an idea we had at the beginning... it's where it all began. You never knew what was going on behind that door. To be immersed in that room where that wonderful boy was born... but also that room where that mindset was created for him to commit such horrendous things.

MORE: The unscripted moment that became a standout scene in Netflix's Adolescence

"Instinctively I took the teddy bear as the last little remnants of my boy. The take you see was the final take that we used. The very last take of anything, my wife and my two kids were there as well. When I went into the bedroom, what they did was put pictures on the wardrobe from them saying, 'We love you, Dad.' That sparked that last final scene in that moment."

Speaking about the ending—where there was no plot twist, just the acceptance that Jamie really did kill Katie—Stephen told Netflix's Tudum that they intended for the audience not to believe that Jamie committed the crime at first: "That was down to the casting. We wanted the audience to be on Jamie’s side and think, ‘Oh my God, this arrest is terrible. There’s no way he's done this.’"