A cloaked raider is picking off Federation shipping bound through the wormhole, and when it turns out to be hitting Cardassian vessels too, Sisko finds himself working with the last people he'd choose as allies to hunt it down. Two of his own crew end up captured in the process, leaving Sisko to balance a rescue against the fragile, furious peace between Bajor and Cardassia.
Summary by Loreful, from public sources