There are two different shows co-existing under the title Torchwood: Miracle Day” (Friday at 10 p.m. on Starz). The first is a classic kind of science fiction story, built around a simple what if? question: what would happen if every person in the world suddenly became incapable of dying? The second is a familiar action thriller in which a rogue team of government agents try to find out who made everyone immortal, and why.

The second show is the one that Starz clearly signed on for when the pay cable channel became co-producer and American distributor of “Torchwood,” which had been a purely British series in its earlier seasons (and aired in these parts on BBC America). It’s a commercial, easy-to-sell idea, one featuring a few characters who will be familiar to hardcore fanboys and girls, as well as recognizable American faces like Mekhi Phifer and Bill Pullman. If this wasn’t a show about Torchwood was investigating the miracle, getting into gunfights and trading banter, it wouldn’t exist.

And yet, even as a fan of the 100% British incarnation of “Torchwood” (particularly the 5-part “Torchwood: Children of Earth” miniseries from 2009), I couldn’t help wishing that “Torchwood: Miracle Day” spent a little more time on the miracle and less on Torchwood.

Our story opens as reviled pedophile murderer Oswald Danes (Pullman) is about to be executed for his crimes. He’s strapped to the table, injected with the necessary chemicals, begins to spasm... but doesn’t die. From that point on, no person on Earth can die, whether they’ve been stabbed, shot, drowned, suffered a heart attack or, in the case of cocky CIA agent Rex Matheson (Mekhi Phifer), get impaled through the heart by a piece of rebar in a traffic accident. The only person who seems to be mortal these days is original “Torchwood” hero Captain Jack Harkness (John Barrowman), a smiling, bisexual adventurer who used to be cursed with immortality himself, destined to never age even as his friends and loved ones grew old and died. (Though the method by which Jack and others accept that he can die are sketchy, at best.)

The miracle isn’t as fabulous as it sounds at first. The sick aren’t magically healed; they just don’t die. Rex’s heart doesn’t repair itself, and he spends the five episodes I’ve seen scarfing down painkillers and collapsing anytime his activity gets strenuous enough for his latest bandage to leak. Diseases spread that ordinarily would have gone away when the host body died, and the lack of death leads to a population boom that threatens to drain the planet’s resources in short order.

The parts of “Miracle Day” just dealing with those unexpected consequences are both fascinating and fun. “Torchwood” creator Russell T. Davies and his writers come up with a variety of macabre fates for characters that are clearly much worse than death itself(*), and they keep the scenes where doctors and policy wonks argue about how to deal with the miracle lively and provocative. (And that’s even though our POV character in those scenes, Arlene Tur as emergency medicine specialist Dr. Vera Juarez, is one of the stiffer additions to the cast.)

(*) And between Jack’s immortal days and an arc in the second British season about an undead Torchwood team member whose body couldn’t heal itself, Davies has already covered this territory a lot without somehow running out of ideas. If you have to have a macabre area of interest, might as well explore it all the way. 

But as an actual narrative about Torchwood - which in its early days was something of a British answer to “The X-Files,” by way of “Doctor Who” (where Captain Jack first appeared) - “Miracle Day” is much more of a mixed bag.

It’s twice as long as “Children of Earth” was, and several times more ambitious. The narrative skips back and forth between the UK and various points in America, and the action and the production values are much more befitting an American series than the budget-conscious UK style. The first episode, for instance, features an expensive car-vs-helicopter chase scene, and later episodes feature the new Torchwood lineup - featuring former British members Jack and Gwen Cooper (Eve Myles, amusingly hard-nosed as always) and Americans Rex and Esther Drummond (Alexa Havins) - infiltrating a series of large and scary facilities connected to the miracle.

Scope and ambition are usually qualities I admire in my TV drama, but there are times when it feels like Davies and company are biting off a lot more than they can chew.

Though "Children of Earth" was dealing with a global threat, it still dealt almost entirely with the small Torchwood team and a handful of people in the British government. "Miracle Day" has a much larger cast of characters - Lauren Ambrose from "Six Feet Under" has a terrific time playing an amoral publicist, and the early episodes feature guest turns from the likes of C. Thomas Howell, Wayne Knight and Mare Winningham - and the much larger canvas of America to play with. 

Davies turns out to have Important Things to say about the US of A, and he says them very loudly and obviously. Rex is a swaggering, provincial bully until the plot requires him to be humbled just enough to work alongside Jack and Gwen. When Dr. Juarez goes to visit a camp set up to deal with the overflow of should-be-dead people who can't care for themselves, the administrator is an unqualified, racist, sexist caricature, with a random Southern twang. A politician argues that the not-quite-dead shouldn't have the same rights as everyone else; naturally, she's identified as a member of the Tea Party. There's an evil corporation (a favorite Davies pinata) involved. Etc.

Now, science fiction has often been used to comment on present-day social and political issues, and if Davies wants to include critiques of American cultural imperialism, corporations run amok, grass roots conservative politics, etc.,(**) that's his right and not inappropriate to this genre. But a lot of the social commentary feels very busy and loud, and it struggles to find a place alongside the conspiracy thriller material.

(**) At the same time, let me remind you that this blog has a No Politics rule. Nobody can discuss this stuff rationally anymore, so any comments with any kind of political bent are going to get deleted, ASAP. Understand?

Also, by packing so much story into each episode - even if there are going to be 10 episodes that run close to a full hour, commercial-free - Davies doesn't always have time to deal with every thread properly. There's a running arc about Oswald Danes going from Public Enemy Number One to a mostly-beloved cult figure, and even though Bill Pullman gives good speech (see also "Independence Day"), "Miracle Day" never quite sells how he makes the transition from villain to messiah.

But even with the busy nature of the story, even if the plot in the episodes I've seen isn't as engaging as the premise itself, "Miracle Day" still has Captain Jack and Gwen Cooper, who remain warm, fun, ingratiating heroes, both separately and together. (And "Miracle Day" is written for the benefit of people who have never heard of "Torchwood" before, let alone seen an episode, so even though it features the two of them and Gwen's trustworthy husband Rhys, references to previous adventures tend to be oblique.)

When Davies introduced "Torchwood" back in 2006, it was sold as an adult sci-fi series, as opposed to the all-ages "Doctor Who." But in those early days, "adult" tended to translate as "everyone has sex with everyone else, regardless of gender or planet of origin." With "Children of Earth," Davies recognized that he could keep some of the racy bits in (even in "Miracle Day," Jack takes time out from saving the world to visit a local gay bar) while also dealing with some genuinely adult, thought-provoking subject matter. In the half I've seen, "Miracle Day" isn't quite as successful at that, but it's not for lack of trying. It aims high, and wide, and near and far, and if it doesn't hit all of its many targets, it hits several. And that's probably enough to justify the time and expense everyone put into bringing "Torchwood" more firmly onto American soil.

Alan Sepinwall may be reached at sepinwall@hitfix.com