The Dominion launch a devestating attack on Vulcan. Odo and Morn's old friend are trapped in a Klingon battle program in the holosuite and together they must fight their way out. An exact replica of Chief O'Brian dies.
The Bajoran homeworld is threatened by a crop blight and asks the Federation for assistance. The discovery of a relic in the Gamma Quadrant confirms the truth of an ancient Bajoran legend. Chief O'Brian dies.
Worf's greeting is interpretted as a marriage proposal by the conductor of a touring Betazoid opera company and Captain Sisko demands help. A mysterious stranger is not what they seem. Chief O'Brian is duplicated in a transporter accident and one of him dies.
An unexpected Klingon election result leads to rumours of a coup. Dr. Bashir is sent on a humanitarian mission, which turns out to have a secret Cardassian military agenda. A version of Chief O'Brian, from a parallel universe, dies.
A teenage member of the Jem'Hadar comes to the station to seek assylum. Captain Sisko travels to a parallel universe and has to convince the parallel version of Dax that they're married. Chief O'Brian is duplicated in a transporter accident and one of him dies.