On Deep Space 9, Rom and Leeta study a PADD with images of various wedding dresses from Tellarite modern to Risian traditional, but have disliked all of them. Ziyal persuades them to let Elim Garak design one for them. Garak tells her that he finds her adoration both "flattering and disturbing". Rom and Leeta see Captain Benjamin Sisko walking along the Promenade and approach him.
Miles O'Brien is telling Sisko that his wife and children have left for Earth due to the dangers of being on the front line. Rom and Leeta ask Sisko to officiate at their wedding that is to be held in three weeks time, to which Sisko agrees. After they leave, Sisko and O'Brien move to one of the Promenade windows where a large crowd has gathered. O'Brien states that "maybe they're not coming", to which Sisko replies "that would be a nice surprise". Suddenly, the wormhole opens and several dozen Dominion starships enter the Alpha Quadrant on their way to Cardassian space. This is the fifth Dominion convoy to enter the Alpha Quadrant in as many weeks. Sisko predicts that an attack will occur soon.
Jake Sisko arrives at his father's quarters for his first home-cooked meal since the last time he visited his father. Sisko curtly hands Jake a PADD, telling him to read the headline. It reads "Bajorans Continue Negotiations with the Dominion", "station commander opposes non aggression pact" and the by-line reads "by Jake Sisko". Jake reveals that this is his first article for the Federation News Service.
Meanwhile Jadzia Dax, Kira Nerys and Odo are in a cargo bay checking several crates. The crates hold several thousand containers of yamok sauce. Kira realizes that Quark has smuggled them in, believing the Cardassians will soon retake the station. Odo asks what they want to do with it, to which Kira makes no reply. Jadzia tells him to dump it. Jadzia asks her what is going on between her and Odo, to which Kira reveals that Odo has feelings for her and that she only found out about a month previously.
As Nog brings Sisko his morning beverage, he asks if the rumors about the Romulans are true. Sisko has no idea what he is talking about and inquires further. Nog tells him that he was talking to several Orion free traders in Quark's the previous night and they said they heard from a Vulcan diplomat that the Romulan Star Empire had signed a non-aggression pact with the Dominion. Sisko tells Nog not to believe the rumors and to remember the one hundred and ninetieth Rule of Acquisition – "Hear all, trust nothing." However, after Nog leaves, Sisko contacts Dax and tells her to put him through to Starfleet Intelligence.
Later, in the wardroom Sisko reveals that the Romulans have indeed signed a non-aggression pact with the Dominion, joining the Tholians and the Miradorn who have already done so. The Bajorans are still debating the pact as they were also recently offered it, but Kira assures everyone that they will never sign it or any form of agreement with the Dominion. Sisko also reveals that Starfleet Command has decided no more Dominion ships can be allowed into the Alpha Quadrant. A minefield will be deployed at the mouth of the wormhole to stop the Dominion convoys. Odo comments that by doing so they could start a war to, which Sisko replies that, since they are losing the peace, a war might be their only hope.
In Dax's quarters, Jadzia, O'Brien and Rom are trying to come up with the best type of mine to deploy in the minefield. O'Brien suggests using pulse mines but the Dominion ships could simply wait at the mouth of the wormhole and destroy them. He then suggests cloaking them, but it would weaken the mines. Rom, while in the midst of complaining about his upcoming wedding, then realizes that if the mines are to be small they will need a lot of power and a way to replace them. Each mine could be equipped with a replicator unit and would swarm detonate, with at least twenty mines homing in on one ship. The main draw back is that the entire minefield will have to be deployed before it can be activated, or premature detonation could occur.
Sisko talks with Starfleet Command and relays their judgment to Kira and Worf that Starfleet's forces are needed elsewhere and will be unable to assist in the deployment of the minefield. Their orders are to deploy the minefield and prepare for a Dominion attack. DS9 will also have to defend the Defiant, as she will be alone while deploying the minefield.
Kira meets with Odo and agrees to his plan of stopping all outgoing communications. They also decide to put their personal feelings for each other aside until the crisis has abated.
The Defiant begins to deploy the mines but the Dominion becomes aware of it almost immediately. A Dominion ship arrives with Weyoun aboard. He leaves behind all of the false pleasantness that he has always used before in his meetings with Sisko, and bluntly issues an ultimatum – remove the mines, or the Dominion will take control of DS9 and remove them themselves.
Sisko stubbornly tells Weyoun that the mines will stay and he will not allow any more ships through the wormhole. Weyoun then returns to his old ways – a mask of reasonableness and sincerity. Weyoun tells Sisko that it is the Cardassians who are pushing for the convoys, saying that they want the security that the Dominion brings. Weyoun then offers to limit the convoys to cargo ships, construction units and civilian aid if Sisko will remove the mines.
Later Sisko tells his senior officers and General Martok that the Dominion will attack as early as tomorrow. He tells them that his conversation with Weyoun was all words and an attempt to lure the other side into a "false sense of security". Sisko did not believe it and is sure Weyoun didn't either. Sisko asks Martok to take the Rotarran to the Cardassian border and watch for the Dominion fleet. Sisko also tells Kira to contact the Bajoran Council of Ministers for an immediate meeting, as he plans to use his position as Emissary to endorse the nonaggression pact. Kira doesn't understand why he would want the Bajorans to sign the pact, therefore Sisko tells her that the only way Bajor will survive the war will be to do what the Romulans did, and sign the pact to keep them out of the fighting. He is convinced that by not doing so, the past five years of their work will be undone.
The Bajorans sign the pact and First Minister Shakaar orders all Bajorans to leave DS9 for their own safety. Kira arranges for Ziyal to stay with several of her friends. Later, Sisko marries Rom and Leeta in a traditional Bajoran ceremony. Rom then tells her to go to Bajor, and not look back.
As Sisko prepares Program Sisko 197, General Martok contacts the station with a report of a large Dominion fleet heading their way. However, his transmission is jammed by the Dominion and Dukat, Weyoun and Damar appear on the viewscreen. Dukat asks Sisko if he wants to surrender and avoid "unnecessary bloodshed". Sisko tells him no, to which Dukat happily replies that he was hoping Sisko would say that. Sisko orders his crew to battle stations.
The Dominion fleet will enter weapons range in twenty minutes. Unfortunately, the Defiant has an hour of work left before the minefield can be activated. Jake helps Doctor Bashir and his medical staff with medkits. He tells Bashir that he promised the Federation News Service a first hand account of the battle. Bashir tells him he will get it and that his name is spelled with an 'I'.
Garak meets Odo on the Promenade, praising his composure and calling him "an island of tranquility in sea of chaos." Odo's entire Bajoran staff has been evacuated to Bajor. Garak tells Odo that during the Klingon attack on the station, almost two years previously, when he and Dukat were defending the members of the Detapa Council, Dukat turned his back to him. Garak considered killing him but realized he could not fight the Klingons by himself. He tells Odo that by the time this day is over, everyone on the station will regret his failure to kill Dukat.
The Rotarran approaches DS9 and Sisko tells Martok to protect the Defiant. Worf then activates the weapons array. Kira arrives in Ops and protests Starfleet's refusal to turn the station over to her government. Sisko notes her protest and Kira reports for duty.
The Dominion fleet approaches the station. On the flagship, Dukat tells Damar he has been waiting for this moment for five years. Damar tells him that they will reclaim Terok Nor and Bajor. Weyoun chastises them, reminding them of the nonaggression pact. The fleet enters weapons range and Dukat gives the order to fire.
The battle begins and the station manages to destroy several Dominion ships plus several that were closing on the Defiant. Damar and Weyoun are surprised that DS9's shields are holding, to which Dukat tells them he has found it wise never to underestimate the Federation's technical skill and Captain Sisko's resourcefulness.
The Defiant comes under attack but is saved by the Rotarran. The enemy fleet targets their weapons on the outer docking ring, penetrating the station's shields. Main power to the shields is lost and the auxiliary power will not last long. However, the Defiant reports in, telling Sisko the minefield has been deployed. Jadzia activates the field and returns to the station. The Dominion fleet prepares for a final assault on the station, with Dukat calling the activation of the minefield a "minor setback". Sisko decides there is nothing more they can do and orders all Federation personnel to evacuate.
As the evacuation begins, Dax says goodbye to Worf, who has been assigned to the Rotarran, and agrees to marry him when the war is over. Sisko addresses the station population who are remaining behind. He tells them that although the station has been lost, the attack on the station allowed the Federation and the Klingons to attack and destroy the Dominion shipyards on Torros III. He also tells them that no victory can make this moment any easier for him, and promises he will not rest until he stands with them again. Sisko is then transported to the Defiant.
Garak is already aboard, and asks Captain Sisko for permission to remain and for once tells the very simple truth – he has no where else to go. Captain Sisko agrees, and heads for the bridge. The Defiant and the Rotarran leave the station, fire a few last shots, and cloak before they can be destroyed.
Kira and Odo arrive in Ops and transmit a message to the Dominion fleet, welcoming them to Deep Space 9. Kira then activates Program Sisko 197, which disables the station.
Quark, removing all aspects of the Federation's presence, tells his staff to break out the kanar and find some yamok sauce. Rom reports for duty in his old job as Assistant Manager for Policy and Clientèle. He is now a spy for Starfleet. As Rom starts work he finds Jake, sitting nearby. He has stayed behind to report on the Dominion occupation. He theorizes that the Dominion will not harm him, the son of the Emissary of the Prophets, lest they alienate their new Bajoran allies.
On the Defiant, Sisko finds out and is angry, but he cannot risk the entire crew for one person, even if he is his son. The Defiant and the Rotarran continue on their course to rendezvous with the Federation/Klingon task force. Nog states that now they will make the Dominion "sorry they ever set foot in the Alpha Quadrant."
Dominion boards DS9 and Odo, and Kira and Quark arrive to meet them. Weyoun tells Odo he is honored that he remained behind. Dukat and Weyoun visit Ops and the station commander's office where Sisko has removed all of his personal items, except one. Dukat finds Sisko's baseball still on the desk, a message from Sisko.
On the Defiant, Sisko sits in contemplation of the impending war that will sweep across the Alpha and Beta Quadrants. The Defiant and the Rotarran de-cloak and move to join the large Federation and Klingon fleet.
The Dominion War has begun.