On Wallach IX, young Valya Harkonnen promises Mother Superior Raquella that she'll 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.
Two Harkonnen sisters combat forces that threaten the future of humankind and establish the fabled sect that will be known as the Bene Gesserit.
Following a tragedy, young Tula worries about being accepted despite her family name; a skeptical Valya struggles with the decision to take the Sisterhood vow; years later, Valya receives a message that confirms her suspicions.
Tula tries to understand the origins of the nightmare that affects all acolytes of the sisterhood; as Tula attempts to understand the acolytes' shared dream, Valya sets her plan in motion to redeem House Harkonnen ahead of the Landsraad.
As Tula contends with the reveal of Desmond's true identity, the acolytes uncover a devastating long-held secret about the Sisterhood.