Smell. Taste. Hearing. Sight. Touch. For those of us with all of our senses intact, we tend to take for granted just how important they are, both collectively and apart, in our day-to-day experiences. Playing undeniable roles in our lives, all of them have the power to unlock memories and contribute pleasure and, occasionally, pain. People who suffer from a loss of any one perception have an automatic handicap, but can easily survive and press on to have a full life. The disappearance of most, or all, of them, however, would be catastrophic. Directed by David Mackenzie (2009's "Spread") with a chilling, matter-of-fact candidness, "Perfect Sense" presents a horrific "what if?" scenario and bravely allows it to run its natural course. A raw, character-centric hymn to the apocalypse, the film reminds of 1999's "Last Night," 2006's "Children of Men," 2011's "Contagion," and 2011's "Melancholia," but brings its own angle and ideas to similar subject matter. The immense empathy Mackenzie and screenwriter Kim Fupz Aakeson afford their characters and the population of the planet as a whole ensures that their interest lies not in the world's destruction, but in the giant, messy beauty of love and existence, and what the human race has to lose if such a nightmarish pandemic were to pass.

Michael (Ewan McGregor) is a London-based chef with commitment issues who still beats himself up over a past relationship he knows he didn't handle well. Susan (Eva Green) lives in the flat across the street from the restaurant, an epidemiologist feeling restless and kind of sad in her currently lonely here-and-now. Upon the two of them meeting, there's a chemistry akin to the strike of a match. They get along amazingly well and seemingly understand each other even in shorthand. Alas, their tight bond is one with either perfect timing or the worst ever. A mysterious outbreak has suddenly begun to sweep the globe, intense feelings of grief paving the way for a person's complete loss of smell. Scientists are baffled over its cause—is it ecological? Biological? Religious? Supernatural?—but when the bulk of the world's sense of taste vanishes overnight, it becomes clear that no one is safe from impending events that will soon, too, strip them of their optical and auditory functions. With nothing left but to feel, both physically and internally, might Michael and Susan still have a chance to be saved by each other?

Engrossing before packing a staggering emotional wallop as its full implications are revealed, "Perfect Sense" dabbles in the soft-spoken and radical, an intense spectrum that makes this very much a universal story rather than a centralized one. Michael and Susan are damaged thirty-somethings. They've made mistakes before and, if given the chance, would probably make new ones in the future. They're also innately good people, just trying to get by. Together, though, they are something more than that. It's an unexpected sensation that sneaks up on them, but how can one deny such a kindred connection? If their lives are about to be ripped apart and imminent death is the only option, at least they might have each other to hold onto until nothingness takes over. This, then, is both the savior and tragedy of the entire picture, the gradual realization that without senses and some kind of palpable reciprocated love, we do not really exist at all. Michael and Susan will, until they're no more. Dust in the wind.

The screenplay—and director David Mackenzie's treatment of it—is much more than just a love story set against the backdrop of doom. If we were to begin systematically losing our senses, yet had to forge a path to keep going, this is how it would probably be. Visionary yet steadfastly logical, the story takes into account everything from the act of dining out when one's taste and smell are gone, to the common need to hear music once sound is no more (the answer to this latter question is miraculous in its unforced comment on the dynamism of human nature). Another scene, in which a food critic rates Michael's cuisine not by the most obvious traits—he can't—but by temperature, texture and presentation, is simple yet immensely clever. While some people rebel and loot, most keep going. To collapse and submit to the end is not a part of our fight-or-flight tendencies.

Ewan McGregor (2011's "Beginners") and Eva Green (2006's "Casino Royale") make for a fervent pair as Michael and Susan, living lives so closely to each other but only meeting recently by pure chance. Their time together, first as new friends getting to know one another and then as more, is not cause for instantaneous love, but more significant of the undeniable binds moving them closer. When they have fallen, it means something, and when they agree to tell each other a sort of secret that few people know, it is their comfort in being honest and bare that only proves how right they are as a couple. It is this knowledge that gives such sudden unforgettable urgency to the last scenes. What happens cannot be discussed, but the enormity of its suggestions hit the viewer like a truck, its concluding moments transformative and electrifying.

"Perfect Sense" is an expert study in paranoia, the fleetingness of one's past, and the memories that make us who we are. It all boils down to the connection between emotions and senses, and the fuse that could so easily short-circuit if one of them cut off. A smell of a room, the taste of lemon, or the aroma of a cold winter's day may snap a person back to a family member no longer with them or a nostalgic vision of childhood. A song can instantly remind of the time a person first heard it. To no longer be able to access these thoughts and senses is indescribably frightening, Michael's and Susan's fates coming down to the compassion and, yes, love they'll be able to hold onto for as long as breath escapes their mouths. "Perfect Sense" captures all of this with the tenderness of a star-crossed romance that ends with an embrace, and the bitterness of it being the last one either of them shall ever take.