Murder in the Cathedral, for which there is an excellent summary on Wikipedia, is a verse play depicting the death of Thomas Becket. Henry II of England (he was married to Eleanor of Aquitaine) had appointed Becket Archbishop of Canterbury, but the two men did not see things the same way after that and Becket was seen as a threat to the King and was murdered on his behalf in 1170.
The play presents a variety of arguments and counter-arguments about the rightness, or wrongness, of Becket's murder. The first argument comes from the chorus (the women of Canterbury) who are speaking for the people who are trying to go about their lives as best they can and fear being caught in the drama between King and Church. This bit makes me think of the hobbits in Lord of the Rings:
"Archbishop, secure and assured of your fate, unaffrayed among the shades, do you realise what you ask, do you realise what it means to the small folk drawn into the pattern of fate, the small fold who live among small things, the strain on the brain of the small folk who stand to the doom of the house, the doom of their lord, the doom of the world?" (part I)
I think what really makes this play powerful is the way that it keeps turning in on its own arguments to bring a different perspective to the forefront. Then, at the end when you think you know who the bad guy was, several players step up from behind the footlights and make their arguments which turns the whole thing around yet again.