“Look at the fire sweeping the bush,” the chorus sings, describing how war is descending on the palace. They watch as Orestes paces inside the palace, looking at Agamemnon’s throne and gripping his bloody sword. “The game’s afoot!” the women cry.
The chorus often has a moment of anticipation prior to the climax in Greek tragedies, and this moment is an example of that convention. Ancient audiences were familiar with the myth of Orestes and Electra, and so they would have known that revenge was forthcoming.