The mirror Jennifer Sisko lures Jake into the mirror universe, and Sisko follows to help the rebels defend Terok Nor in their new Defiant.
Jennifer Sisko's counterpart visits the station and takes Jake back to the mirror universe, and Sisko follows. The rebels have taken Terok Nor and captured the Intendant, and need Sisko to help the mirror O'Brien complete a copy of the Defiant before the Alliance strikes back.
Jake bonds with Jennifer as a mother he lost. Commanding the rebel Defiant, Sisko drives off the Alliance fleet led by the Regent, the mirror Worf. The Intendant escapes, killing the mirror Nog and Jennifer, leaving Jake and his father grieving her once again.