It is 1957, and twelve men have been led into a jury room of a New York City court of law. They are given final instructions about determining the verdict in a murder case whose defendant faces the death penalty if found guilty. Before deliberations begin, the men take a short break after filing into the hot and stuffy room. They gather around a long table to begin discussions about the case. The defendant, a young man, is accused of killing his father; and, after a preliminary vote, all but one of the jurors presume he is guilty. Juror #8 is the only one who feels differently. Because they must come to a unanimous decision, debates begin.