It’s dinnertime in a war zone, and “Bridge Over Troubled Water” crackles over the radio. A family, upstage around a brightly lit kitchen table, drinks bouillon as a lost son, alone and far away, buries his head in his arms in the dimness downstage.

Slowly, all but the lost one begin singing along with Simon and Garfunkel, and a sense of warmth and safety buoys the scene nearly into a full-fledged musical number. The feeling lasts only seconds before it’s obliterated, but its sweet, comic absurdity is exactly the point.

The best moments of “The Devil on All Sides,” a French play about the war in the former Yugoslavia, are like that: a collision of humor and horror. They are also rare. Though it allows music to transcend and laughter to puncture the extravagant ugliness of war, there is a heavy-handedness to Fabrice Melquiot’s script. Ben Yalom, who translated the play, directs its frustratingly uneven production at P.S. 122.

Mr. Melquiot places love and ethnic loyalty at the center of his tale, which fairly vibrates with outrage at the violence of a conflict that ended only a dozen years ago.

Lorko (Joseph William) is a young Serb married to Elma (Nora el Samahy), a Muslim. Once the war begins, their mixed marriage lands him in prison, where his Serbian captors beat him, torture him, and force him to repeat vicious lessons: “Croats deserve to die, Muslims to die.” As a reward once he is sufficiently compliant, he is ordered to the front line. “When you leave, you can kill, pillage, rape,” a prison guard tells him. “You’ll learn who you are.”

Elma remains at home with Lorko’s parents (Debórah Eliezer and Stephen Jacob), his brother, Jovan (Brian Livingston), and his childhood friend, Alexander (Ryan O’Donnell), whom the family has taken in as one of its own.

War invades their house through the dreams and then the lives of Jovan and Alexander, who sign on eagerly to kill and maim even as news comes that Lorko is a deserter. Comforted that he is at least alive, his mother knits ceaselessly, desperately hoping that her bits of wool can mend what’s torn and keep her children safe.

Large-scale tragedies of any kind, however, have a stubborn habit of remaining abstract to outsiders. Too often, Mr. Melquiot simply states the facts of war’s atrocities: its killing and maiming, its inevitable sexual violence and destruction. Hearing about them in a monologue is not so different from hearing about them in a news report, and it is human nature to tune it out when war becomes old news. It does not help that the mouthpiece for these monologues, Mr. William, who exhibits depth and considerable charm when playing off another actor, goes flat on his own.

The play primarily belongs to Lorko and the other young men at war, and Mr. Livingston and Mr. O’Donnell are fine as zealous soldiers. Ms. el Samahy, whose mellow, melodic singing voice is one of the production’s great assets, is a steady presence as Elma. Ms. Eliezer and Mr. Jacob are near-ciphers in the two-dimensional roles of Lorko’s parents, but they practically emit sparks in smaller, more richly written roles.

The play, though, is most hobbled by its myriad natures, which Mr. Yalom is unable to reconcile. In theory, stark drama, satire, magical realism, and theater of the absurd can coexist. In life, they sometimes do. But here they spar with and obscure one another, most harmfully in the character of Alexander, a violent Serbian bigot who is made to represent all violent Serbian bigots. Mr. Melquiot draws him as a menacing cardboard figure and a buffoon — except when he chooses, far too late, to display his human vulnerabilities.

Until July 1 (150 First Ave. at East Ninth Street, 212-477-5288).