A coded Cardassian signal from the Gamma Quadrant sends Garak and Worf after Enabran Tain, and reveals a Dominion fleet poised to invade.
When the station picks up a coded Cardassian message from the Gamma Quadrant, Garak admits it is a distress call from his mentor Enabran Tain, thought lost in the failed attack on the Founders. Sisko lets Garak go after him with Worf. Inside a nebula they find a massive Dominion fleet massing for an invasion, warn the station and are captured.
In a Dominion prison camp they find the dying Tain, who acknowledges Garak as his son before he dies, along with General Martok and the real Dr. Bashir, proving that the Bashir on the station is a Changeling. Sisko tries to seal the wormhole, but the attempt has been sabotaged and Dominion warships begin pouring through. It is the first of two parts.