The Federation faces the Dominion's growing alliance.
The Breen announce their alliance with the Dominion by attacking Starfleet Headquarters on Earth. On Bajor, Dukat persuades Kai Winn to study the forbidden Book of the Kosst Amojan. Her aide Solbor discovers that her companion is Dukat, and when he threatens to expose them, Winn kills him; his blood reveals the book's hidden text.
The Dominion then strikes back at Chin'toka, and a new Breen energy-dampening weapon helps hand the allies one of their worst defeats; the Defiant is destroyed. Afterwards Damar publicly declares a Cardassian revolt against the Dominion and opens it by destroying a Vorta cloning facility, and Sisko sees the rebellion as a possible key to victory.