WARNING: The following article contains spoilers for the Castle Rock Episode 9 "Henry Deaver," now streaming on Hulu.
"Go, then. There are other worlds than these."
Those were the last words to come out of Jake Chambers 'mouth as he slipped away into the dark abyss near the end of Stephen King's The Gunslinger. Jake's ominous declaration would go on to haunt Roland for quite some time, until he realized just what the boy meant when he saw him in the second entry of King's The Dark Tower cycle, The Drawing of the Three. The revelation of Jake not only being alive, but existing in a different world/timeline was earth-shattering in the narrative of the novels, and it's later explained that the protagonist, Roland, saves Jake from being killed in his original timeline in 1977, thus creating a paradox and fracturing Jake's mind... and his own.
Jake had explained to Roland that his death was what let him to the Mid-World in the first place, but when the Gunslinger averted the boy's demise, the timelines became too much for either of them to process, and the fractured memories of them folding in on one another began to drive them mad.
Stephen King is no stranger to creating alternate realities and doppelgängers. He's had entire novels based on time travel, metaphysical nightmares, and other-worldly horrors, but what makes The Dark Tower special is how the existence of multiple Jakes takes a toll on the fabric of reality.
Now, Castle Rock is playing with the same notion. In the penultimate episode of the season, "Henry Deaver," we discover that "The Kid" (Bill Skarsgard) is more than just some ageless monster. He is, in fact, Henry... but not our Henry (Andre Holland). "The Kid" is from a different world, a world beyond the veil in which Ruth and Matthew Deaver conceived a son instead of adopting one. So before this gets any more confusing, let us refer to Andre Holland's character as Henry Prime and Mr. Skarsgard's character as Alternate Henry.