In the first two scenes of Act III, Hamlet and Claudius both devise traps to catch one another’s secrets: Claudius spies on Hamlet to discover the true nature of his madness, and Hamlet attempts to “catch the conscience of the king” in the theater (III.i.582). The play-within-a-play tells the story of Gonzago, the Duke of Vienna, and his wife, Baptista, who marries his murdering nephew, Lucianus. Hamlet believes that the play is an opportunity to establish a more reliable basis for Claudius’s guilt than the claims of the ghost. Since he has no way of knowing whether to believe a member of the spirit world, he tries to determine whether Claudius is guilty by reading his behavior for signs of a psychological state of guilt.