Madness in great ones must not unwatched go.

– William Shakespeare

Hamlet, Act 3, Scene 1. Claudius is referring to Hamlet here and his unpredictable behaviors. But in an ironic way this also refers to the behaviors of Claudius, who murdered his brother, stole the throne and married his brother’s wife. His madness must also not go unwatched. And it doesn’t, by Hamlet, who kills him.