“A Perfect Day” opens Friday at Sundance Cinemas. R, 1:46, two and a half stars out of four.

War is hell, and cleaning up afterwards is no picnic either.
That’s the message coming from “A Perfect Day,” a black comedy that’s the English-language debut from Spanish writer-director Fernando Leon de Aranoa (“Mondays in the Sun”). The film is set in the Balkans during the 1990s, but focuses not on those who fought in the conflict, but humanitarian aid workers who came from other countries to help the innocents caught in the middle.

If the phrase “humanitarian aid workers” makes you think of saintly, touchy-feely types, think again. The workers in the film fall into two camps – grizzled, cynical lifers who seem more at ease helping strangers than sustaining real relationships, and wide-eyed newbies who aren’t yet wise enough to know they ought to be cynical.
Falling squarely in the former camp is Mambru (Benicio Del Toro), a world-weary worker who is about a week away from finally leaving the aid-worker game for good. His partner is B (Tim Robbins), even more grizzled than Mambru, who tools around listening to punk rock mixtapes. At one point, B comes across a dead cow in the middle of the row, and explains to his new recruit (Melanie Thierry) that guerrillas have likely mined the road either to the left or the right of the cow. But which side? (B’s solution is to drive over the cow.)
Mambru and B comes across a well that contains the body of a very large, very dead man. The well is the only source of drinkable water for nearby villages, and if the body has time to decompose, it will poison the water.
So Mambru and B spend the rest of the movie roaming the countryside looking for a good piece of rope to haul the body out. That’s a taller order than one would think in such a bombed-out country, and their quest brings them in contact with U.N. peacekeepers, black-market opportunists, armed children and Mambru’s disgruntled ex-lover (Olga Kurylenko).

There are some effective moments here and there, whether bits of comic business between the aid workers (Robbins is especially funny as the strangely cheerful B), or moments where the horror of ethnic cleansing suddenly surface. Not a shot is fired in “A Perfect Day,” but the aftereffects of war hang in the air, in the bombed-out buildings, hastily-marked graves and haggard faces.
But the film tries to go a long way on just atmosphere and no story; while de Aranoa’s refusal to sentimentalize or soften these hardened observers is admirable, it means that none of the characters change much over the course of the film. He seems torn between making a straight character study and making larger points about the horrors of war. We see lots of shots of the aid workers’ two trucks hurtling back and forth across the landscape, and the movie often seems to be just as aimless.