On Wallach IX, young Valya Harkonnen promises Mother Superior Raquella that she will protect the Sisterhood by putting one of their own on the Imperial Throne. Thirty years later, Valya faces a threat to her long-awaited plan.

While Valya recruits Theodosia to help manage the situation on Salusa Secundus, a reluctant Tula enlists Lila for a vital mission.

Before becoming known as the Bene Gesserit, a powerful Sisterhood works in the shadows to guide the universe.

All acolytes of the sisterhood have the same nightmare. Tula tries to understand its origins. Before the great meeting of the Landsraad, Valya plans to rehabilitate House Harkonnen.

While Tula tries to keep her secret project from being discovered by the other Sisters, Desmond goes on a warpath to root out insurgents.

As Tula confronts her true identity, Valya's manoeuvres draw her into a confrontation with Desmond as his power grows.