I have heard,
That guilty creatures sitting at a play
Have by the very cunning of the scene
Been struck so to the soul that presently
They have proclaimed their malefactions;
For murder, though it have no tongue, will speak
With most miraculous organ.

– William Shakespeare

Hamlet, Act 2, Scene 2. Hamlet has heard that guilty people watching a play have been so affected by the performance that they have confessed their crimes. So he decides to put on such a play for his uncle, to test the truth of the Ghost’s claim that he is his father’s murderer.