There were a number of reasons why I liked "World War Z," the film based on Max Brooks's book of the same name. First, it was a competently made thriller and not simply a stringing together of whiz-bang CGI effects. Secondly, it presented a positive image of a father. In a time when Homer Simpson and Peter Griffin are the norm for fatherhood in the popular culture, Brad Pitt's character, Gerry Lane, is actually a man of intelligence, deep compassion, and self-sacrificing courage. But what intrigued me the most about "World War Z" is how it provides a template for thinking seriously about sin and salvation.

As the movie opens, an ordinary American family is alarmed by news of a mysterious contagion that is spreading quickly across the globe. In a matter of days, the disease has reached their hometown of Philadelphia, and they are forced to flee. It becomes clear that a virus is turning people into the walking dead, hungry for human flesh. What is particularly frightening about this iteration of the zombie myth is that the undead of "World War Z" are not the lumbering oafs that we've come to expect, but rather are fast-moving, teeth-grinding, extremely focused killing machines.

After a series of close calls, Gerry and his family manage to escape and make their way to a ship off the eastern seaboard. We learn that Gerry had been a special operative for the United Nations, skilled in fighting his way in and out of hot spots around the world. His superiors draft him back into service, charging him with the task of finding out how to contain the virus. Accompanied only by a small team of scientists and military personnel, Gerry wings his way first to Korea and then to Jerusalem, where, at least for the moment, the Israeli government has managed to keep the zombies at bay behind a high and thick wall. Now when Jerusalem came into focus, I realized that the filmmakers perhaps had some ambitions beyond simply another ringing of the changes on the zombie story.

One of the more thought-provoking assertions of the sixteenth century Council of Trent is this: original sin is passed on from generation to generation, "propagatione et non imitatione" (by propagation and not by imitation). What the fathers of Trent meant is that sin is not so much a bad habit that we pick up by watching other people behave, rather, it is like a disease that we inherit or a contagion that we catch. A newborn inheriting a crack addiction from his mother would be an apt trope for the process. If it were simply a matter of imitation, then the problem of sin could be solved through psychological adjustment or mental conditioning or just by trying harder. But if it is more like a disease, then sin can be fully addressed only through the intervention of some medicine or antidote that comes from the outside. Moreover, if sin were just a bad habit, then it wouldn't reach very deeply into the structure of the self; but were it more like a contagion, it would insinuate itself into all the interrelated systems that make up the person. The fathers of Trent specify that sin causes a falling-apart of the self, a disintegration of mind, will, emotions, and the body, so that the sinner consistently operates at cross-purposes to himself. Do you see now why the zombie--a human being so compromised by the effects of a contagion that he is really only a simulacrum of a human--is such an apt symbol for a person under the influence of sin? And do you see, further, why the erection of a mighty wall would be an utterly unsuccessful strategy against such a threat? Indeed, one of the most memorable scenes in "World War Z" is of the zombies swarming over the walls of Jerusalem.

A bad habit might be solved by a teacher, but a disease requires more radical treatment. I won't burden you with all of the plot details, but Brad Pitt's character figures out that the zombies are dissuaded from attacking if they sense in someone a deadly disease. Accordingly, he enters a lab, protected by a veritable army of zombies, in order to inject himself with a noxious contagion. Having done so, he is able to walk among the undead unmolested, and from his blood, an antidote can be produced for the world. Now one would have to be inattentive in the extreme not to notice the rather clear Christ symbolism at play here. Gerry does not fight the zombies on their own terms; rather, he enters courageously into their environment, takes on a deadly disease and then, through his blood, offers a cure to suffering humanity. St. Paul said that, on the cross, Jesus became sin so that "in him we might become the righteousness of God" (2 Cor. 5:21); and "in him we have redemption through his blood" (Eph. 1:7). Jesus becomes the healer (Soter in Greek, Salvator in Latin), precisely in the measure that he enters the world of sin, even to the point of shedding his blood, and explodes it from within.

The great story of salvation is still in the intellectual DNA of the West, and that is why it pops up so regularly in the popular culture. And perhaps this is happening precisely because the Christian Churches have become so inept at relating the narrative. To those who don't know this fundamental story well, I might recommend a thoughtful viewing of "World War Z."

Father Robert Barron is the founder of the global ministry, Word on Fire, and is the Rector/President of Mundelein Seminary near Chicago.