The premiere episode of "Constantine" aired Oct. 24 on NBC. Reviews are mixed, and the ratings are less than stellar, but Matt Ryan playing the titular character shows some promise. Some viewers have criticised the manner by which John Constantine appears to be toned down version of DC Comics' Hellblazer.

Spoiler alert: This update recaps the highlights of Constantine Season 1, Episode 1. Read at your own risk if you have not watched the series opener.

Titled "Non Est Asylum," the pilot episode of NBC's Constantine begins at the Ravenscar Psychiatric Facility. John Constantine (Matt Ryan) checks himself in, hoping to find remedy for his desolate situation after a failed exorcism, in which a girl named Astra was murdered by a demon called Nergal.

At the asylum, Constantine releases a demon, which left a threat: "Liv Die." Constantine then tries to warn Liv Aberdeen (Lucy Griffiths). There were some trust issues, until John shows Liv her father's pendant.

Constantine Season 1, Episode 1 also introduces Charles Halford as Chas Chandler, Constantine's friend. He is a reliable cab driver and ingenious supernatural specialist.

The premiere episode's demon is called Furcifer. It derives its power from electricity. Furcifer brings up Astra in an attempt at making a deal with Constantine, but the trick was botched by Liv's pendant. Liv later leaves town, passing on her scry map and pendant to Constantine.

Griffiths received mostly positive reviews for her portrayal of Liv, and many viewers are disappointed that she has been cast only as a guest star. This, however, opens many possibilities for the TV version.

Also receiving optimistic reviews after the broadcast of Constantine Season 1 premiere is Harold Perrineau as Manny, the angel watching over Constantine. Toward the end of the episode, Angélica Celaya is introduced as the artist Zed Martin.

Between Constantine and Chas, and with the inclusion of Manny, there is much that writers could do to still pull the skeptics in. Constantine Season 1, Episode 1 has at least established John Constantine's darkness and quirks, albeit he is a somewhat milder antihero than Hellblazer of the comics.

"Game of Thrones" director Neil Marshall ("The Watchers on the Wall") makes a strong visual case, but teleplay writer Daniel Cerone could use more remarkably compelling lines. The pilot story was developed by series developers Cerone and David S. Goyer.

Those unfamiliar with Hellblazer or even the 2005 movie could find the characters and their quests entertaining, if they are constantly given sharp lines and strong visual appeal that caters not only to comic book fans, but to the niche viewers, too.

It is too soon to tell whether the ratings of Constantine is any indication of its success or failure. It is difficult not to note, however, that Constantine drew a weaker rating than "Dracula" did.

"The premiere of NBC's "Constantine" averaged 4.34 million viewers and a 1.4 key demo rating," Hitfix reported. In contrast, the same report said the premiere episode of Dracula "averaged nearly 5.3 million viewers."

Hellblazer was launched by DC Comics in the '80s, before turning it over to its Vertigo imprint in the '90s. The character was created by Alan Moore and Stephen R. Bissette. Keanu Reeves portrayed Constantine in the movie of the same title, released in 2005.

WATCH: Constantine Season 1, Episode 2 Preview | NBC Promo Video on YouTube ('The Darkness Beneath')