"Monsters" is one of the top cinematic achievements so far this century. That is not to say it is necessarily a great film, only that, for what was achieved on a reported budget of less than $100,000, it is very nearly mind-blowing. The auspicious writing-directing debut of Gareth Edwards (who also pulls off cinematographer and visual effects duty), "Monsters" was made with a crew of two behind-the-scenes people, two actors, and a lot of glorified extras. Its stunning production values and almost seamless computer-generated effects work make it look as if its budget were seven hundred times as large, putting to shame plenty of big studio films that cost $100-million-plus.

A cross between 2004's "The Motorcycle Diaries," 2005's "The War of the Worlds," and 2009's "District 9" with plenty of 1934's "It Happened One Night" thrown in, "Monsters" is, collectively, like no other feature film in memory. Set in a world where a space probe in search of alien life crashed upon re-entry over Central America, infecting a portion of Mexico with giant roaming creatures, Andrew Kaulder (Scoot McNairy) is a professional photographer in search of that one outstanding shot that will win him a magazine cover. Roped into escorting his boss' grown daughter, Samantha Wynden (Whitney Able), from Costa Rica to transportation that will send her safely to the U.S., Andrew quickly discovers this trip is going to be tougher than expected. When their train announces it is turning back, Andrew and Samantha hop out and make their way to a ferry station. Tickets are $5,000 apiece—money they barely have—and the only other option is to take their chances traveling across the "Infected Area" toward the American border. As the two of them bond over a tough situation and develop feelings for each other, they inch ever closer to an unavoidable revelation and fate.

From the outside—and based on its marketing campaign—"Monsters" looks to be a sci-fi/horror effort about two people being stalked by alien invaders across an apocalyptic landscape. Instead, it's a road movie and a love story that just so happen to take place amidst a horrific backdrop. The invasion occurred six years ago and, for the residents of Mexico, life has almost gone back to normal (save for the occasional destruction of a building or two). Most of the creatures are confined within the "Infected Area" bordering North America and are only glimpsed a few times throughout. Because they are so sparsely used yet constantly looming ominously over the story, when they make their appearance it's so jolting and realistic that the impact is truly disconcerting. The conceptual design of the creatures and the visual effects used to bring them to startling life are close to photorealistic, made even more impressive because they were rendered on director Gareth Edwards' own computers for next to no money. If ever there was proof that movies no longer require enormous budgets in order to have an enormous scope, this is it.

Andrew and Samantha start off as strangers with only one connection—her father and his boss—but as opposed to not getting along at first they hit it off fairly well. Samantha is engaged to be married, but that doesn't stop her from feeling jealousy (that she none too convincingly hides) when she discovers Andrew has had a one night stand the evening before she is to set sail through the hot zone. As they are isolated further and must rely solely on each other to make it to the border, the film increases in quiet intimacy to the point where one begins to question the very title of the movie. The sights and sounds Andrew and Samantha are faced with are filmed with a lonesome poeticism, but that doesn't always take away the fact that this is a deliberately paced movie requiring patience and trust that director Gareth Edwards knows where he's going. He does.

Scoot McNairy (2005's "Herbie: Fully Loaded") and Whitney Able ("All the Boys Love Mandy Lane," still unreleased in the U.S. as of this writing) are the sole human attractions in a cast otherwise made up of walk-ons and a lot of open land. They are well-equipped in their roles, natural and never showy. Their romantic chemistry is admittedly about room temperature, but they do come off as opposites who unexpectedly connect on a deeper level under strenuous circumstances. In an amusingly accurate exchange, Samantha asks photographer Andrew how he feels about relying on bad things happening in order to profit from it, to which Andrew replies, "You mean like doctors?" Later, when they come within sight of the man-made structure separating Central America from Texas, they comment how different it is to look at America from the outside. It's a little on the nose, but a testament to who they are and how good they never realized they had it.

Simmering with tension the closer Andrew and Samantha move toward their destination, "Monsters" culminates in the sort of confrontation between man and alien that audiences will have been waiting for all along. Not one to go down an oft-traveled road, Edwards upholds his end of the bargain by veritably spooking the viewer—a shot in which one of the creatures looms over a nighttime gas station, lit only by lightning flashes, is astoundingly nightmarish, reminding of something out of H.P. Lovecraft—but then jerks in a different last-minute direction that finds a compassionate commonality between man and beast. Not feeling the need to answer every question posed, "Monsters" is, at once, rousingly independent and technically very much a part of the mainstream. What it isn't is conventional, the final image all the more tragic if one has paid close attention to the picture's prologue. Suddenly, all that has come before is put into perspective. "Monsters" is adamantly uncompromising—a certain attentive commitment is demanded of the viewer—but what is destined to be its biggest claim to notoriety is how much money it makes $15,000 seem like. All of Hollywood ought to be green with envy.