At the end of the Cretaceous period, 65.5 million years ago, a meteor entered the Earth's atmosphere at 44 miles per second. A fireball ten miles in diameter, it struck the tip of the Yucatan Peninsula, unleashing a billion times more force than the atom bomb that vaporized Hiroshima. This extinction event that killed the dinosaurs (and ripened the world for mammalian conquest) is easily envisioned as a white hot flash. Or perhaps as cyclonic winds, buffeting skeletal remains.

But the meteor's impact only annihilated life within a 300 mile radius. Earthquakes, tsunamis, volcanic eruptions and wildfires seized the rest of the Earth's inhabitants in short order. And while creating chaos, these were mini-disasters compared to the trillions of tons of dust and gas that shot into the atmosphere. With the sun obscured, global winter descended. Photosynthesis ground to a halt. Without plants to eat, herbivores died first, followed quickly by the carnivores that preyed on them. Quickly, that is, on the geological scale. The mass die-off of land animals actually took centuries. Aquatic creatures (sharks and crocodiles among them) and shrew-sized, insectivorous mammals survived as scavengers.But in imagining this hellish world of acid rain and flood-flattened jungle, the human mind walks an anthropomorphic tightrope. That misery and terror stalked the animal survivors, while the other seventy percent of life rotted around them, feels like a fact set in stone. To ask whether or not this stressful existence changed their fundamental characters, as races or individuals, is to ask too much.What we can do, in the thought experiments of literature and drama, is explore how humans might face their own extinction event. Comic book scribe Robert Kirkman does so enthusiastically in his series The Walking Dead. Begun in 2003 by Kirkman and artist Tony Moore, the black and white Image publication gives us a world overrun by shambling hordes of strangers, co-workers and loved ones. The comic is also the basis for an AMC TV series of the same name, which enters its third season in October.This is wonderful news, for both comic and horror fans. The Walking Dead features incredible writing and acting, traits shared with AMC siblings Mad Men and Breaking Bad. Its stellar production value is second only to HBO programming (A Game of Thrones, Boardwalk Empire). The Walking Dead's Season 2 finale had 9 million viewers, making it the most watched telecast in basic cable history.Say what? A single episode of a zombie show, based on a comic book, drew 9 million people? If voodoo wasn't responsible, then high-octane creativity must be pounding through this concept's veins. A look at the comic will explain much- it's mission statement, featured on the back of more than a dozen graphic novels, grips you by the shoulder, looks you in the eye, and lists the sharpened facts:

How many hours are in a day when you don't spend half of them watching television? When is the last time any of us really worked to get something we wanted? How long has it been since any of us really needed something that we wanted? The world we knew is gone. The world of commerce and frivolous necessity has been replaced by a world of survival and responsibility. An epidemic of apocalyptic proportions has swept the globe causing the dead to rise and feed on the living. In a matter of months society has crumbled. No government, no grocery stores, no mail delivery, no cable TV. In a world ruled by the dead, we are forced to finally start living.

Superficially, these have been the parameters for a "zombie apocalypse" since director George A. Romero's seminal films Night of the Living Dead (1968), Dawn of the Dead (1978) and Day of the Dead (1985). Kirkman, more a student of the genre's human element than its splatter, owes Romero much for the bones of his creation. But in the meat of his execution, the comic writer has proven relentlessly innovative, using the monthly magazine format to tell zombie tales that far outpace the complexity and emotional depth of a two hour film. In his The Walking Dead: Days Gone Bye introduction, Kirkman says:

For me the worst part of every zombie movie is the end. I always want to know what happens next. Even when all the characters die at the end... I just want it to keep going. More often than not, zombie movies feel like a slice of a person's life shown until whoever is in charge of the movie gets bored. So we get to know the character, they have an adventure and then, BOOM, as soon as things start getting good... those pesky credits start rolling.

Kirkman's opus (just over 100 issues long so far) is the journey of Rick Grimes, a sheriff's deputy in Cynthiana, Kentucky, a small town where curtailing teen mischief pays most of his bills. When a high-speed chase ends in a shootout, Grimes is hit in the chest and rendered comatose. Later, waking in a hospital, he initially finds it empty of visitors and employees. Then, after encountering a single, decayed corpse, Rick opens the barred doors of a cafeteria. Dozens of the living dead see him and attack.And because this isn't a two hour film, these zombies don't need to run, as most have since director Danny Boyle's revolutionary 28 Days Later (2002). Kirkman and his briskly-shuffling dead buck this decade's trend of sprinting zombies, bolstering the idea of a rotting world slowly constricting humanity. The coke-addled mayhem in Zach Snyder's 2004 Dawn of the Dead remake is thrilling, but ultimately cheap compared to the strangulating allure of Kirkman's saga.Building from this deadly-serious tone, The Walking Dead introduces a cast hoping to reestablish some semblance of normal life. Once Rick is armed and mobile (first in a car, until the gas runs out, then a horse, until it's eaten), he meets the young scavenger Glenn, who brings him to a camp of nearly two dozen survivors. He explains, "We've got some cars for shelter... and we all take turns keeping watch at night. We figure if we stick close to [Atlanta] they'll be able to find us when the government sorts all this mess out." At the camp, Rick reunites with his wife Lori and son Carl. Shane, his law enforcement partner, is also present, filling a badly needed leadership role.In fleshing out these characters, Kirkman effortlessly dresses the gore with dramatic dialogue. Aided by Moore, who has a knack for uniquely drawn faces conveying believable emotion, the survivors routinely steal the zombies' thunder. In one scene, Shane tries to comfort Lori while Rick searches for supplies. He approaches from behind, in the rain, and says, "Staying out here isn't going to make him come back any sooner. I'll keep you company." She shrugs off his touch, replying, "Don't. You've got to stop. Rick is back now... he's alive... and he's my husband. You've got to stop this." Shane then reminds her that, while believing Rick dead in a zombie-infested hospital, they slept together. "That night was a mistake," answers Lori.Kirkman lets this morsel simmer some. He and Moore follow with practical scenes, like Rick showing members of the camp how to shoot (including, to his wife's chagrin, young Carl), and the chopping of firewood. Later, as the survivors enjoy a cozy campfire meal, two of their own become dinner during a zombie attack. This brings the rivalry to a boil between Rick, who wants to search for a safer location, and Shane, who wants to stay and wait for the army. They argue on and off, sometimes explosively, for days. When Shane finally punches his former partner, in front of the entire camp, he loses everyone's sympathy.Dispatch by zombie would seem to be the elegant, desired solution to the Shane problem, especially after he runs into the woods alone. It's certainly the fate an average film, with little investment in the characters, would serve audiences. But Kirkman and company want nothing to do with average. They have Rick follow his friend into the woods. Shane then turns his shotgun on our protagonist, spiraling into a dreadful rant: "I thought I could make it... I thought I could hold out... wait until [the army] came and rescued us. They would have brought us nice beds and hot showers... We were going to be okay!""We still are," Rick says, "everything's going to be fine." His cheeks tear-stained, Shane utterly disagrees. He blames his partner for returning after Lori and Carl had mourned him, and for subsequently taking them back. But before Shane can murder Rick, a bullet rips through his own neck."Don't hurt my daddy again!" Carl screams, still holding the gun. As Shane topples and bleeds out, father and son embrace. The boy whispers, "It's not the same as killing the dead ones." Rick replies, "It never should be, son."Such a remarkable scene would be ratings gold for The Walking Dead TV show, which was developed by moody spellbinder Frank Darabont (The Shawshank Redemption and The Green Mile). But marketing savvy has wrought curious narrative mutations in the AMC production. There are story changes meant to surprise those already familiar with Kirkman's world. This means the scenery, the character arcs, and (most importantly) the plot denouements remain true, but the roads to each twist fabulously, allowing the comic and TV show to stand as distinct experiences.The biggest (and best) difference between the two is that Shane lives beyond the first storyline. Played with gruff deliberateness by Jon Bernthal, AMC's version of the character dogs Rick's leadership as the group leaves the original campsite and heads for a Center for Disease Control facility. There, a lone doctor named Jenner (who isn't actually in the comic) shows them scanner footage of a brain resuming baseline activity after death. Jenner (Noah Emmerich) has lost faith in civilization's return, and records messages for colleagues around the world who never answer. He further tells Rick and company that if he hasn't yet devised a cure, nobody will. Before the group leaves, the doc whispers something to Rick (the hawk-eyed Andrew Lincoln) that we can't hear.Season 2 addresses this mysterious message, but it remains deep in the background until the last few of the thirteen episodes. By this point, fans of the comic watch because of the show's many titillating differences (like when your favorite band performs, delivering acoustic or up-tempo deviations on familiar songs). Season 2 opens on a Georgia highway covered in abandoned vehicles. To Rick's group, traveling in a few cars and a Winnebago, this is both a barrier and chance to shop. But as they rifle through the belongings left by people fleeing Atlanta, a herd of zombies passes through.It's a stunningly tense sequence that no modern movie would dare. The shambling dead, or "walkers" as the group calls them, drift among the cars like hundreds of slow-motion pinballs. Our heroes, caught off guard, scramble under vehicles and try to remain calm. Sophia, a young girl Carl's age, doesn't. She bolts as walkers notice her, down the highway shoulder and into the woods. When Rick catches up with her, hiding her beneath an embankment to lure some persistent dead away, the relief is temporary. Sophia bolts again.Finding Sophia, to the frustration of viewers unappreciative of classic suspense, takes up half of Season 2. And though it's not a plot from Kirkman's comic, it leads impeccably to one that is. While searching for the girl, Rick, Carl and Shane come across a deer. Rather than shoot it for food, the men allow Carl, transfixed by the living creature's majesty, to approach. When a stranger shoots the deer (from off screen), the bullet zips straight through, hitting Carl in the ribs.This scene exemplifies the show's dramatic routing of the comic. There's a small symphony of reasons for this, mainly that the comic, for all its inventiveness, can feel improvised, with bramble-like events growing hither and yon. The show, more carefully timed and budgeted, prunes these micro-plots, giving the most important events more space to flower. And with Kirkman producing AMC's production, it continuously receives fresh input from the creative wellspring.Carl's shooting in Season 2 overlaps with events in the graphic novel Miles Behind Us. The trigger-happy stranger, Otis, leads the group to a securely fenced-in farm. Run by a veterinarian named Hershel and his adult children, the bucolic shelter glows with hope for Rick and the survivors. Hope dims, however, when the older man says that once Carl is healed, they must move on. Then, within a few episodes, we find that the God-fearing Hershel believes the zombies are merely sick, and that a cure will be found for them. Locked in a barn is his undead wife and extended family, along with neighbors and other loose walkers found in the countryside. This news rips Shane and Rick apart as effectively as any meat-starved mob. Shane, naturally, wants to clear the barn with a shotgun. Rick insists that they follow the latter-day James Herriot's rules, to stay in his good graces and possibly live on the farm.None of this helps the increasingly desperate search for Sophia. That the doll she carried has been found by a stream is heartening. That the group begins to tie their belief in her safe return to Rick's leadership isn't. Then there's the outspoken Dale (Jeffrey DeMunn), who tries to hide their gun supply in the woods. When Shane catches him, the older man says, "This world, what it is now, this is where you belong. And I may not have what it takes to last for long, but that's okay. 'Cause at least I can say when the world goes to shit, I didn't let it take me down with it."

The Walking Dead's moaning, gnashing and severed heads might remind us of films we grew up snickering at, but it's as serious as dramas come. The tone is dusky, severe, and stays that way. There's no triteness. No schlock. And in their absence, brilliance has bloomed.More tight, shock-filled storytelling awaits when it returns to television this month. Kirkman's comic, still the source of eminently wonderful tales, hints at Rick's people mixing with criminals behind the barbed-wire of a prison. If this sounds soapy, think on whether or not we wouldn't do the same as the world ends. Jenner said, "This is what takes us down. This is our extinction event."____ Justin Hickey is a freelance writer living in Boston and completing his first science fiction novel.