Here's the finale of Childhood's End explained - and why season 2 is unlikely. Childhood's End is a three-part science fiction miniseries based on the novel by Arthur C. Clarke. This 1953 book revolves around the arrival of a seemingly benign alien race dubbed the Overlords, who slowly transform Earth into a utopia. They eliminate disease, war and poverty, but over time, their true intentions are revealed. Childhood's End is considered one of Clarke's best works, and an adaptation spent decades in development hell.
Stanley Kubrick considered adapting Childhood's End in the 1960s but decided on Clarke's 2001: A Space Odyssey instead. Other adaptations were mooted in the decades that followed, with Kimberly Peirce (Carrie 2013) once attached to a version developed by Universal during the early 2000s. It finally came down to SyFy to take on the Childhood's End book in 2015, which remained remarkably faithful to the original text while delivering on its haunting ending.
The Childhood's End miniseries split the story into three episodes while updating the book for modern viewers. The miniseries cast Charles Dance (Game Of Thrones) as Overlord supervisor Karellen, who chooses farmer Ricky (Mike Vogel) to serve as his representative. The first episode sees the Overlords subvert most sci-fi tropes about alien invaders by quickly eliminating war, pollution and other concerns for humanity, and while there are plenty of humans distrustful of the aliens and their "benign" rule, many take to the era of peace they help usher in. There's also the fact they're unwilling to actually show themselves to humanity, stating they're not ready yet.
Events ramp up in Childhood's End episode 2 when Karellen finally reveals himself over a decade after the Overlords' arrival - and he's shown to look very much like a Christian depiction of The Devil. Childhood's End final episode "The Children" reveals the children of the world born after the alien's arrival are undergoing stranges changes, including telekinetic powers. The finale also sees Ricky succumb to a long-brewing illness, and rejecting an offer from Karellen to spend an eternity in a dream projection with his late wife Annebelle.
A major subplot of Childhood's End finale found main character Milo (Osy Ikhile) stow away on an alien ship to get to the truth behind the changes happening to the children. When he reaches the home planet of the Overlords he learns about The Overmind, the cosmic intelligence of the universe. It turns out the "invasion" was about preparing the children's consciousness to shed individuality and become one with the Overmind. Milo arrives back on Earth - which was an 80-year round trip due to time dilation - and finds it a post-apocalyptic ruin, with the children having already ascended. Karellen gives Milo the chance to leave with them, but he decides to stay behind as the last true human, and the planet is destroyed.
This is the same ending as the Childhood's End novel and a memorably haunting one. Of course, it also makes a second season extremely unlikely - and more so, unnecessary. Unless it's some kind of prequel set before the planet's destruction, there's no more story to tell, and it's best off as a one and done sci-fi parable.