Julian notifies Captain Sisko that Chief O'Brien has been out of touch for three days. The Chief had been searching for the wife of a former Orion Syndicate member who he had helped capture ("Honor Among Thieves"). His last known location was New Sydney, where, coincidentally, Ezri's mother has quite a bit of influence since she runs a mining operation in the sector. After three years away, Ezri finally returns home to see her family and learn whatever she can about the whereabouts of O'Brien.
When the Cardassian occupation of Bajor ended in 2369, the mining space station Terok Nor was left abandoned, its systems ripped out. By invitation of the Bajoran provisional government, Starfleet stepped in to oversee the rebuilding and day-to-day operations of the newly christened Deep Space Nine.
The years of Starfleet's nonintervention into Cardassian matters, however, had taken its toll on relations with the Bajorans. Consequently, Starfleet's position was a tenuous one; many Bajorans, suspicious and hostile as a result of decades of Cardassian oppression and brutality, did not greet the Federation's presence with open arms. The Federation's assistance is put to the test as DS9 becomes a center of travel and commerce that stretches into the Gamma Quadrant.