Apparently the wormhole keeps opening and closing randomly - Dax can't work out why. Meanwhile, Odo is furious because someone has moved all his furniture. Apparently Dax liked breaking in while he's asleep and shifting his furniture by a few centimetres. What a CARD!
Meanwhile Star Fleet has reported that a high-level Federation/Romulan conference on Earth has been blown up, and Worf has spotted evidence of a Changeling in the footage.
Odo makes Dax move all his furniture back before he departs for Earth with Sisko. Sisko lets his dad know he's coming - his dad owns a restaurant in New Orleans, which has presumably recovered from Katrina by then. Jake is unimpressed that they might be staying with grandpa because he always makes Jake peel potatoes. Bashir and O'Brien are doing a Battle of Britain holosuite program. O'Brien's accent is impressive. He asks Odo to visit his folks in Dublin, and Odo says he's worried about how he'll be received on Earth.
On Earth, Sisko and Odo meet up with Admiral Leyton, who appoints Sisko acting head of Star Fleet security. Wow.
Sisko and Jake retire to Grandpa Sisko's restaurant. Sisko observes his father's lost weight, despite the fact the doctors told him he should keep his weight up (he's a transplant patient). Also Nog pops in for a dinner of tube grubs, and is edgy about how he's doing in Star Fleet academy. He tells Jake he's having trouble fitting in.
Sisko visits Federation President Jaresh-Inyo, who's concerned about disrupting the population and isn't convinced the problem is that concerning - until Odo shapeshifts from Sisko's case. Sisko outlines some new security measures he's worked out. They start installing phaser arrays in rooms. Nog asks to talk to Sisko - he wants to join Red Squad, an elite squad of cadets.
Sisko returns to New Orleans. Jake's visiting a school in New Zealand? I thought we were a penal colony in Trek times. :P Sisko tells his dad off for not having seen a doctor for eight months.
Leyton doesn't seem very impressed with Odo, but then it turns out Leyton is a Changeling. It gets away by turning into a seagull. The real Leyton meets with Odo, Sisko and Leyton's assistant to discuss this deeply troubling event, and then Jake rings up his dad to say Grandpa's in trouble.
Sisko rushes down and finds his father's refusing to take a blood test to determine if he's really human. Sisko and Jake take the test first to show him it's all right, but he still refuses, asserting his rights. Then Grandpa accidentally cuts himself, and catches Sisko staring at the blood, suspicious that his dad is a shapeshifter. He rants at length and then collapses.
Later Sisko angsts about how he couldn't trust his own father, and Odo gives him a pep talk.
That evening, Earth's entire power grid goes down. Apparently no one's heard of redundant systems.
Sisko beams to the President's office and suggests declaring a state of emergency, because a Dominion fleet is probably on the way. After a great deal of convincing, the President declares martial law and Federation troops begin covering the planet. TO BE CONTINUED!