The story and action of the play is a steadily rising action as the sniper goes through the motions of trying to cover his company from the rooftop on which he has stationed himself. He becomes aware of another sniper on another rooftop, ends up shooting and killing a soldier below and a woman informant. The action continues to rise as he finds himself in a duel with the other sniper who shoots and wounds him in the arm.
He has to find a way to draw the other sniper out so he lifts his cap on the end of the rifle and pretends to be dead when the other sniper shoots the hat. Once the other sniper comes out, he kills him with a revolver.
The plot diagram would appear to be falling after this, as it seems to be the climax, but the true climax comes only after he goes down to the street and finds that the other sniper was his brother. O'Flaherty leaves the resolution to the reader without giving any hint as to the sniper's reaction to knowing he killed his brother.