Westworld Season 4 just made possibly the biggest reveal of the entire season in Episode 4, "Generation Loss," which changes everything for the series going forward. Much like the epic reveal of the Man in Black being Dolores' beau William from Season 1, which established the existence of two different timelines in the series, Westworld changed the game once again and revealed that humanity is now under the crushing boot of Dolores' corrupted copy that possesses the body to Charlotte Hale, played by Tessa Thomspon. And at the heart of this crushing revelation, Aaron Paul's Caleb, who suffers a devastating heartbreak when he realizes what this means for his daughter Frankie.
In the episode, it is revealed that Caleb has actually been dead for decades and was killed when he and Maeve (Thandiwe Newton) attempted an unsuccessful raid on a new Delos theme park set in the Roaring '20s, with similar storylines to the original Westworld we all know and love. Charlotte Hale has won and has infected the human world with parasites that give her control over their actions and memories much like they are hosts, reversing the roles between the two groups.
The hosts are now in control of the world, and the major city that Charlotte operates in is basically the theme park Westworld on a larger scale; this is the timeline we've seen with Dolores (Evan Rachel Wood), who is now known as Christina and works as a storyline writer for a video game developer.
This is also the same timeline where Bernard (Jeffrey Wright) has woken up in with an omniscient knowledge of future events, based on his time in the Sublime where he's run countless simulations in hopes of learning how to save the world. We found out that he has been in the AI "heaven" for decades and has awoken in the world that Charlotte controls, and the rebel he and Ashley have allied with is a grown-up Frankie – the child that Caleb left behind when he passed away.
As for Caleb, his story exists in the past and takes place shortly after the events of Season 3 when he destroyed the controlling AI known as Rehoboam. We see the events of Caleb's death, though the episode makes it seem as though he has survived. But in reality, Charlotte has just made a copy of his brain and body, turning him into a host that she can torture for mysterious reasons.
Charlotte has been torturing Caleb for over 20 years, and we find out that his daughter Frankie has grown up to become a major figure in the rebellion against Charlotte's dominion over humanity. Now Bernard has joined the fold and has revealed they have a secret weapon in the fight to stop Charlotte – the preserved body of Maeve, who was thought to be destroyed in the same raid that resulted in Caleb's death.
Westworld Season 4 airs new episodes every Sunday at 9 pm ET on HBO.