The drama depicts a jury forced to consider a homicide trial. At the beginning, they have a nearly unanimous decision of guilty, with a single dissenter of not-guilty, who throughout the play sows a seed of reasonable doubt. The story begins after closing arguments have been presented in the homicide case, as the judge is giving his instructions to the jury. As in most American criminal cases, the twelve men must unanimously decide on a verdict of "guilty" or "not guilty". (In the justice systems of nearly all American states, failure to reach a unanimous verdict, a so-called "hung jury", results in a mistrial.) The case at hand pertains to whether a young man murdered his own father. The jury is further instructed that a guilty verdict will be accompanied by a mandatory death sentence. These twelve then move to the jury room, where they begin to become acquainted with the personalities of their peers. Throughout their deliberation, not a single juror calls another by his name because the names are unknown to the jurors. Several of the jurors have different reasons for discriminating against the defendant: his race, his background, and the troubled relationship between one juror and his own son.