It's probably for the best if some paths never cross. A blood-borne South American virus and the humans it turns into super-strong, ravenous cannibals, for example. Or, less melodramatically, an 800-page tome tracking the end of the Anthropocene over nearly a century and the storytelling conventions of network television. It's not that a rough facsimile of one can't be made inside the other. But given the limitations of the form, and the existence of viable alternatives, the effort seems doomed to be mutually unsatisfying—for the creators who want to do their source material justice, and for the fans who want to see it brought to life.

Justin Cronin's 2010 novel The Passage, the first volume of a trilogy that concluded in 2016, is a sweeping, ambitious take on the vampire myths that were then a staple of pop culture, thanks to YA series like Twilight and cable shows like True Blood. An erstwhile Iowa-trained literary novelist whose previous efforts centered on interconnected families and a Maine fishing camp, Cronin's first genre attempt features flourishes like newspaper articles as narration and nearly a dozen disparate parts. It's amusing to read contemporary reviews bemoaning Cronin's betrayal of high-minded realism for the crass, commercialist world of postapocalypse fiction. If only critics knew the book was destined to become a prime-time drama on Fox.

Adaptation is a fraught undertaking to begin with, but The Passage has followed an arduous path to the screen, even by the torturous standards of Hollywood development. Ridley Scott's production company, Scott Free, optioned the rights for an eye-popping seven figures more than a decade ago, years before The Passage was published or Cronin had even finished writing it. When the intended film trilogy never came to be, Scott Free changed strategies and pursued a television series instead. The pivot made a certain amount of sense: Rather than condense thousands of pages into just a few hours, The Passage could translate into a medium as expansive as its story. And in the time since The Passage was first conceived, television had changed enough to seem like a plausible home for the high-concept, inevitably high-budget endeavor.

The Passage's most obvious predecessor is Game of Thrones, itself the product of a wildly complex series of novels that demanded, and received, a massive investment of resources from its eventual home. Commercially, HBO's wager has paid off many times over; perhaps more surprisingly, showrunners David Benioff and D.B. Weiss have also stayed faithful to George R.R. Martin's nuanced, subversive commentary on various fantasy tropes, even if their approval rating has started to flag in later seasons. Game of Thrones in turn raised the bar for networks hoping to mimic its success, and opened the floodgates for storytellers to chase their onetime pipe dreams. The Passage exists in a world made possible by Game of Thrones—and, to a lesser extent, The Walking Dead, whose zombie hordes recall Cronin's "virals," the results of a government experiment gone awry who eventually overtake the planet.

But what The Passage must contend with that Game of Thrones, The Walking Dead, or even a more muted dystopia like The Handmaid's Tale does not: the relative confines of network television. Thrones caps off its pilot with attempted child murder; Handmaid's can open its second season with a ritualized mass hanging in the ruins of Fenway Park. When the hero of The Passage wants to express his shock in a way that is compliant with standards and practices, he exclaims, "Holy ... dammit!"

Some of the decisions that writer Liz Heldens (Boston Public, Friday Night Lights, The Orville) makes in simplifying and streamlining The Passage for television are common sense. Cronin's original narrative spans nearly a century, from the virals' origins as part of the secretive, allegorically named Project Noah to a future when they've converted or eliminated the vast majority of humanity. Heldens's rendition, at least in the three episodes of it provided to critics, slows down and focuses exclusively on Project Noah, a quest for total immunity run out of a converted hotel in Colorado. The adult convicts previously used as inmates aren't leading to any breakthroughs, so Noah's coordinators turn to something much more radical, and controversial: a child.

Stripping away the "post" part of a postapocalypse gives The Passage room to breathe, plus saves some of the juiciest—or bloodiest, depending on your appetites—material for future episodes, or even seasons. Other changes, however, have less to do with making The Passage work for television than making The Passage work for the kind of television it is. Where Noah was originally a military effort to develop a race of super-soldiers, here it's a much more sympathetic attempt to ward off an epidemic of avian flu. And if that doesn't make Noah's scientists sympathetic enough to serve as protagonists, The Passage adds a wife dying of Alzheimer's to serve as extra motivation. We're far from Westeros now.

The Passage is a product of its environment in many other ways: The lead actor is Mark-Paul Gosselaar, last seen anchoring the Padres on the dearly departed Pitch, as federal agent Brad Wolgast, the type of tender-hearted, gruffly competent male authority figure who perennially anchors about 80 percent of CBS's lineup. While present in the novel, The Passage makes the damaged-man-cute-kid bond between Wolgast and 10-year-old Amy Bellafonte (Saniyya Sidney) its emotional centerpiece, like Two and a Half Men with half-baked epidemiology. The sets look relatively cheap, the special effects slightly hokey. The aesthetic is more Buffy than Westworld, albeit much more self-serious.

Network television remains a viable artform, one with strengths its rival cable channels and streaming services could stand to learn from. Broadcast continues to produce a steady supply of affable, deceptively easy-going sitcoms, plus procedurals that balance episodic structure with more prolonged conflicts—both arts that TV's newcomers have yet to master with any kind of consistency. But The Passage is not an office farce, nor a hospital drama. It's a supernatural epic, one that makes sense only as a network endeavor in a time before there was a host of viable alternatives. Watching The Passage is inseparable from wondering what The Passage might look like if it had taken one of those other routes—like the one Y: The Last Man, another tale of near-future cataclysm, is taking at FX, though in fairness, the network may be full up on imaginative vampire shows at the moment. The Passage is a cautionary tale about forcing an unnatural match between organism and host. It's instructive, if not for the reasons its creators think.