The Killer opens on an empty, bare stage. Suddenly the stage is brightly illuminated with blue and white lights, which gives an impression of silence and peace. This is the Radiant City, an enclave within the “dark and dismal” metropolis where Berenger lives.

Berenger, an ordinary, middle-aged man, enters to see the Radiant City; he hopes to move here. He is accompanied by the Architect, who later turns out to have a variety of other civil servant duties. Berenger is enraptured by the City, whose climate is controlled by concealed ventilators; flowers always bloom, it never rains, and the residential villas are built of the finest materials. Berenger finds in the City an embodiment of earlier momentary experiences he has had, sudden euphoria of joy and conviction; at first his pleasure in this new environment is ecstatic, only occasionally punctuated by the dry comments of the Architect. Using a telephone that he carries in his pocket, the Architect becomes increasingly irate about the tardiness of his secretary, Dany. When Dany finally arrives, Berenger falls instantly in love with her and proposes. She pays little attention to him; berated by the Architect, she resigns and leaves.

Berenger now realizes that the Radiant City is deserted. Stones from an invisible source are thrown at him and the Architect; the Architect explains that, in the ornamental pool in the City, one or more people, lured there by the Killer, drown each day. Disillusioned, the idealist Berenger leaves with the Architect; the lighting reverts to the gray of the surrounding city, and, now at a bistro, Berenger and the Architect have a glass of wine and a sandwich. The Architect, who—like other civil servants—is safe from the Killer, explains how the Killer lures a victim to his death by pretending to be a beggar and offering to sell the victim a variety of objects from his basket, everything from artificial flowers to obscene drawings to a photograph of a colonel; finally, at the edge of the pool, the Killer gives the client a push so that he falls in and is drowned. The Architect reveals that his former employee, Dany, has just become the latest victim. Overcome, Berenger resolves to stop the Killer, and rushes off, leaving the indifferent Architect in the bistro.

Act 2 takes place in Berenger’s squalid apartment. Outside, partially visible through the window, are various city people—Berenger’s irritable concierge, truck and car drivers, a grocer, old men, a postman, and so on. Berenger returns from his visit to the City and discovers that, concealed in the dark of his apartment, his friend Édouard is awaiting him. Édouard is ill, has a withered arm, and is carefully guarding his briefcase. Berenger is still agitated about the death of Dany and about the Killer, but Édouard indifferently explains that everyone already knows about the Killer. As they prepare to depart for a walk, the briefcase opens and its contents are scattered. These objects turn out to be the same goods with which the Killer was attempting to interest his prospective victims. There is also an address book in which the Killer’s victims are listed. Unconvincingly, Édouard explains that the Killer had wanted him to publish his diary in a literary journal. Berenger rushes out, with Édouard reluctantly accompanying him, to take the briefcase to the police; in their haste, however, they forget to take the briefcase with them.

Act 3 begins with a political rally conducted by a grotesque Fascist figure called Mother Peep; her followers are called “Mother Peep’s Geese.” She harangues them:We won’t persecute, but we’ll punish, and deal out justice. We won’t colonize, we’ll occupy the countries we liberate. We won’t exploit men, we’ll make them productive. We’ll call compulsory work voluntary. War shall change its name to peace and everything will be altered, thanks to me and my geese.

Berenger, followed by the diffident Édouard, discovers that Édouard’s briefcase has been forgotten, but several other briefcases appear, owned variously by an old man, a drunk man, and even Mother Peep herself. There are battles over the possession of the briefcases, but none of them contains the paraphernalia of the Killer. Mother Peep and her gang disappear, to be replaced by a hectic traffic jam directed by two giant policemen, who refuse to aid Berenger in finding the prefecture. Suddenly they, too, disappear, as do Édouard and the other characters, and Berenger is alone. It is twilight, and Berenger begins to walk toward the police station.

The final long scene of the play, an extended monologue by Berenger, now begins. The scene presents the encounter between Berenger and the Killer himself, a nondescript, one-eyed little man who does nothing but chuckle at each of Berenger’s arguments, threats, and pleas to end his killings. All argument proves useless. Berenger takes out pistols, but he decides that they are powerless against the implacable will of his opponent. He lays down his weapons; the Killer, carrying a knife “with a large shining blade,” and still chuckling, continues to advance toward Berenger, and the play ends.

Throughout The Killer and other plays by Ionesco there is a contrast between, on one hand, light, evanescence, and energy, and, on the other, dark, heaviness, and fatigue. This ambiguous polarity between light and dark is a matter both of philosophy and of theatrical technique. The Radiant City, where the Killer drowns his victims, is brilliant with a sinister light, while the metropolis itself is oppressively heavy and earthbound. The play ends, when Berenger meets his inevitable fate, in twilight, a modulation which provides a sense of closure.

There is also a contrast between the individual and the masses, as there is between a bare stage and a stage full of people and objects. The setting is minimal in act 1, where almost the only visible objects are the chairs and table at the bistro, but in act 2 (in Berenger’s squalid, overstuffed apartment) material objects crushingly abound. By the end of the play, setting and properties virtually disappear, as one by one Berenger’s arguments against death become deflated and even silly, until there is nothing left. Berenger’s increasing isolation in the play is emphasized by his inability to communicate with all the people to whom he speaks. In most of act 1 Berenger is alone with the Architect, but in most of acts 2 and 3 the stage swarms with dozens of vociferous people: passersby outside Berenger’s apartment, throngs of the faithful in Mother Peep’s audience, soldiers, and police. At the end, Berenger is once again alone with the Killer, and he meets his death in solitude—indeed, the chuckling, wordless Killer may be part of Berenger (who cannot stop talking) himself.

As in all Ionesco’s plays, everything is exaggerated, dreamlike, surrealistic. The policemen are giants on stilts; the confusion of the crowds and the traffic is a Kafkaesque nightmare. One of the main inspirations for Ionesco’s plays is the unsophisticated theater of vaudeville, music hall, circus, and Punch and Judy shows. The malevolent energy of Mother Peep recalls the last of these, while the nonsensical jokes and illogical insistence of other characters derive from the other forms of popular theater. Abrupt changes, pointless surprises, bizarre displacements of normal literary continuity make up the dreamlike texture of the play. It is, in fact, a nightmare play, and like a nightmare its apparent absurdity conveys basic, irrational fears.