A terrorist attack on Earth leads to a security crackdown.
After a bomb in Antwerp kills 27 people at a conference, evidence points to Changelings, and Sisko goes to Earth with Odo and Jake. Admiral Leyton gives Sisko charge of security on Earth, and they urge the president to take tougher measures. Sisko visits his father Joseph at his restaurant in New Orleans.
Nog, now at Starfleet Academy, wants to join the elite Red Squad. A Changeling is found posing as Leyton, and Joseph refuses blood tests. When Earth's power grid goes down, the president declares a state of emergency, and Starfleet troops appear in the streets.