IT: Welcome to Derry begins with a series of showstopper sequences that are so audacious they make the second half of the season look downright timid.

In just two episodes, the prequel series and expansion of Stephen King's masterpiece delivers on every expectation of thrills, terrors, and demented delights. It's so effective, in fact, that when the show slows down to explain itself, IT loses some of the mystery and power the inexplicable terror of those first hours has fostered.

Which isn't to say IT is in any way a disappointment. It is not. At best, IT ranks high among the best King adaptations around. Especially as the series gleefully pushes every boundary of good taste.

Set in the 60s, at the height of the Cold War and the civil rights movement, Welcome to Derry is the story of another group of children and adults who peek beyond the veil to discover the cosmic horror creeping on our doorstep. As children go missing in the sleepy town, a group of unlikely friends band together to find answers. Meanwhile, the military is hard at work searching for something buried in the lands once held by native tribes, all who know more than they're letting on.

The big picture plays like a mix of all the best Stephen King elements. There's a little bit of The Body, a lot of IT, some The Shining, and the most invested will even spot allusions to The Dark Tower. It's a series that is both a celebration and exploration of everything we love about this world that, for the most part, works even when it goes off the beaten path.

Where the series falters most is in how it treats horror itself. IT was always scariest when King refused an easy explanation. Fear lives in the unexplainable. It perverts what we accept as fact. When we can give terror a name and weakness, it automatically becomes something to overcome through rules and logic. In the beginning, where it feels like we can't wake up from a nightmare, the series is so scary I had to take long breaks between episodes just to regroup myself.

There is a scene involving the classic monster under the bed trope that is so deeply unnerving that it gave me nightmares. Here, Welcome to Derry taps perfectly into King's mixture of the real and unreal, and those chilling moments where the two intersect.

It's when Welcome to Derry introduces an entire episode dedicated to just explaining itself, the series loses something vital. It gives away the mystery, which is somehow worse than a disappointing ending. Once we know, we can't un-know, and there's a loss of innocence to that which , once lost, only works against the material.

Welcome to Derry survives the fumble thanks to a uniformly strong cast. As with anything featuring magic or otherworldly power, it's the players who sell the illusion. We have to believe that they believe what they're seeing. Thankfully the series rests on the shoulders of the hypnotic Chris Chalk, who seems unable to give a bad performance. Here, he takes on the role of Dick Hallorann, famous for his role in The Shining. How and why Hallorann joins the IT universe is a mystery best left unexplained, but like most things about the expanded King mythology, it somehow works without too much friction.

As with Dr. Sleep, one of the best King adaptations around, Welcome to Derry is at its best when it deals with the ethereal parts of King's lore. Ka, the wheel, the connections that bind us through life and death, all come into play well before the series bogs itself down with rules and restrictions. In one of the best moments of the season, Hallorann shows us just how deep the darkness goes, and the implications are so terrifying they resonate through King's entire oeuvre.

Welcome to Derry is meant to run for multiple seasons, each traversing backwards in time to an origin point for all the horror that plagues the town. I'm not entirely sure that's the best thing to do with this material, but here we are. For now, IT remains a mystery, and that's always for the best. So far, the series has given us a glimpse into tantalizing darkness. There's no reason to and shine a light into it any further.