Leto awaits the arrival of his current Duncan Idaho in the vast subterranean catacombs beneath his Citadel. Possessing extraordinary sensory perception that detects pheromones and posture down to the finest detail, Leto reflects on the political anxieties of the Spacing Guild, his vast hoard of melange, and his own physical transformation beneath a membrane of sandtrout skin. As Duncan descends into the dim, atmospheric chamber, Leto observes every minute detail of his appearance, clothing, and scent. He knows full well that the ghola carries an Ixian lasgun concealed in his briefcase and harbors deep-seated suspicions that he is about to be replaced after sixty years of service.
During their tense interview, Duncan questions Leto about Siona, who has recently escaped with Citadel plans and journal volumes, and brings up a newly discovered cult of Alia on Giedi Prime. Leto remains outwardly bored by Duncan's political paranoia while mentally wandering through ancestral memories and philosophical musings on the predictable, repetitive nature of all rebellions and human chaos. Through careful guidance and sharp questioning, Leto leads Duncan to realize that the Giedi Prime cult is merely a smokescreen used by the Bene Gesserit to locate a hidden Harkonnen melange hoard, transforming Duncan's perceived security threat into an obvious economic reality.
The conversation ultimately deteriorates as Duncan struggles with his conflicting loyalty and the heavy burdens of his repeated historical existence. Prompted by deep-seated doubt, anger, and the belief that the regime must be ended, Duncan suddenly draws the lasgun and aims it directly at Leto. Utilizing the powerful Atreides Voice to shatter Duncan's focus for a split second, Leto launches his massive worm-body from his Royal Cart in a violent, blindingly fast assault. In the ensuing struggle, Duncan is fatally crushed and his lasgun fires, burning a portion of Leto's flipper before the sandtrout skin quickly seals the wound. Duncan dies whispering Siona's name, leaving Leto alone to ponder the close encounter, the vulnerabilities of his decentralized biology, and the enduring tragedy of his companions.