The first season of the Hulu series "Furious" has concluded, revealing that Catherine (Lola Petticrew) was responsible for the death of her best friend, Isabel (Larissa Campos). Series creator Liz Meriwether explained that this twist, which centers on themes of trauma and memory, emerged during the writing process.

In the season finale, it is revealed that Isabel died as a result of complications from childbirth after being sexually abused by Jay Easton (Peter McRobbie). Jay left Isabel to bleed out in his panic room. Emma Easton (Hope Davis) then brought Catherine to Isabel, who, in immense pain, asked Catherine to administer a fatal dose of heroin from a nearby table. Catherine tearfully complied, a moment that left a significant imprint on her character, as she had previously stated she lacked feeling in her hands and could not recall why.

Following Catherine's actions, Emma flees the scene. Alice (Emmy Rossum), after being shot by Emma earlier, confronts Jay Easton. She kills him by severing his oxygen supply after he refers to her as "the movie star," referencing a video of her as a child. Alice later visits Catherine in prison, confessing her actions and revealing she knows what Alice did.

The season ends with Alice watching the childhood video of herself and accessing a list of accounts that have downloaded it, foreshadowing a potential revenge storyline for her character in the second season.

Meriwether stated in a preseason interview that the decision for Catherine to be the one to inject Isabel came about after the first two episodes were written. "It came out in the writer’s room, this idea of memory, her piecing together the memories that she had of what happened to her," Meriwether said. "So in a way, it’s not a whodunit, it’s the story of a serial killer trying to figure out why she’s killing so many people."

Hulu has renewed "Furious" for a second season. Meriwether envisions it as a continuation exploring another significant case, while Rossum is more focused on the internal evolution of her character, Alice, particularly after her actions against Jay Easton.

"I think Alice and Catherine are people who have been underestimated and are both feeling somewhat powerless, even though they’re on these missions for justice and vengeance," Rossum commented. "And when Catherine later on says that killing someone is power, it’s taking power back, I think that that changes something in the way that Alice thinks about what Catherine is doing."