A Cardassian lockdown program is triggered by accident.
While working in the old ore processing area, O'Brien and Jake accidentally trigger a Cardassian security program designed to stop a Bajoran uprising during the occupation. The station goes into lockdown, and each attempt to stop the program triggers another countermeasure, including poison gas and a self-destruct countdown.
Dukat beams aboard to bargain for a Cardassian garrison, but his own superiors had built in a trap to stop him leaving, so he is caught too, as is Garak. Odo and Quark are locked in Odo's office together. Sisko and O'Brien finally boost the station's shields to absorb the self-destruct blast and save the station.