In a windowless Harkonnen room, Baron Vladimir Harkonnen displays a luxurious globe of Arrakis to his Mentat, Piter de Vries, and his nephew Feyd-Rautha. The Baron calls Arrakis the greatest mantrap in history because Duke Leto Atreides is being forced by Imperial order to exchange Caladan for a world where the Harkonnens have prepared his destruction.

A message arrives from Duke Leto refusing the Baron's offer of a meeting. Leto addresses the Baron coldly, accuses him of treachery, and invokes kanly, the formal vendetta. The Baron accepts that the ritual forms have been satisfied, while inwardly noting that Piter is dangerous and may need to be killed once no longer useful.

The Baron and Piter argue in front of Feyd-Rautha, revealing both their mutual distrust and the Baron's purpose in summoning his nephew: to teach Feyd about power, control, and the limits of even a trained Mentat. Piter presses the Baron about promised spoils, especially Lady Jessica, while the Baron reminds Feyd that Piter's brilliance is compromised by emotion, cruelty, and heavy spice use.

Ordered to explain the campaign, Piter lays out the Harkonnen plan. House Atreides will arrive at Arrakeen, where Thufir Hawat will expect a trap; the Harkonnens will plant diversions, including an apparently genuine attempt on Paul Atreides' life. Although Dr. Yueh is the true Harkonnen agent, Hawat will be misled toward suspecting Lady Jessica, a deception meant to impair his judgment and fracture Atreides trust.

Piter then reveals the decisive blow: after staged uprisings distract and reassure the Duke, Yueh will act and the Harkonnens will attack with their own forces reinforced by two legions of Imperial Sardaukar disguised in Harkonnen livery. The Baron warns Feyd that this secret would unite the Great Houses against the Emperor if exposed, but it also gives House Harkonnen an enormous opportunity for wealth, CHOAM power, and renewed control of Arrakis.

The conspirators also account for possible Atreides escape routes, including flight toward the Fremen, which Piter says is blocked by the planetary ecologist Kynes. The Baron savors the fact that the Great Houses will know he destroyed House Atreides and that Duke Leto will understand who caused his doom. Having finished the lesson, the Baron emerges from shadow, revealing his suspensor-supported bulk, and casually orders Feyd to send for food.