The Way of the Warrior, Part I: The Klingon fleet turns up at DS9 to cause trouble, and Sisko calls in Worf to find out what's going on.
The station is being searched for a Changeling. Sisko and Kira stumble on it, but it gets away. They corner it on the Promenade, and it turns out to be Odo - they're conducting a drill. Quark offers to cut him in on bets re how long it'll take to catch him next time. Later, Sisko has a dinner date with Kasidy Yates, for presents him with a cap with her brother's baseball team's insignia on it. Of course, they're interrupted by Dax calling Sisko to ops.
The Klingon flagship carrying General Martok has turned up to request shore leave. As soon as Sisko grants it, the rest of the Klingon fleet decloaks. Ooops.
Yay, pepped-up title sequence!
Martok meets with Sisko and Kira, and has a round of cutting themselves to prove they're not Changelings. Then Martok announces the Klingons have come to help defend the Alpha Quadrant against the Dominion.
Odo and Garak chat about how the Cardassian empire has closed its borders. The pair interrupt a couple of Klingons hassling Morn. Later on, Garak encounters a bunch of Klingons in his shop and is beaten up. After Bashir patches him up, Garak muses over why the Klingons beat him up, and concludes they must have mistaken him for someone else.
DS9 receives a distress call from Kasidy's freighter saying they're under attack. Sisko rushes over in the Defiant to find that a Bird of Prey under the command of Captain Kaybok has the freighter in a tractor beam so they can search it for Changelings. As this is in violation of Bajoran law, Sisko forces Kaybok to release the ship.
Later, Dax reports that the Klingons have withdrawn to unclaimed space so they can do what they want. Martok drops by to drop a dagger on Sisko's desk and swear a bit - Dax says Kaybok's been killed for disobeying orders. Sisko decides to call in reinforcements in the form of Worf.
Worf's been at a Klingon monastery since the Enterprise was destroyed, and has been thinking of resigning his commission, but is happy to help out. Worf retires to Quark's bar, where he amuses the Ferengi by asking for prune juice, and gets introduced to Bashir and the game of darts. Enter Kira and Dax in medieval dress, who are arguing over Kira having punched out Sir Lancelot. Then there's some Klingons, and Worf starts off by provoking a fight with Martok's son, Drex. Worf wins, of course, and steals the kid's knife, then goes back to his quarters to unpack. Martok turns up to get his son's knife back and gets a speech about honour.
Dax finds Worf trying out her Klingon exercise program, and the pair duel for a bit with Bat'leths. Dax suggests there must be a Klingon or two around who owes his family a favour. Fortunately, there is! Worf learns the Klingons are planning to attack Cardassia as there's been a recent coup which they think was engineered by the Dominion.
Sisko confronts Martok and says that the Federation will not condone an attack on Cardassia, and such an attack will jeopardise the Federation/Klingon treaty. After Martok beams off the station, the Klingon ships all set off for Cardassia.
The DS9 staff discuss what to do. Worf thinks it's just an excuse for the Klingons to have another war. If they sit back and do nothing, the Klingons might attack them next, to gain control of the wormhole, and if they warn Cardassia, they may provoke a Klingon/Federation war anyway.
They solve the problem by Sisko asking Garak in to measure him up for a new suit while the senior crew discuss the coming attack. Garak, naturally, warns Cardassia.
Sisko reports that Star Fleet command has condemned the attack, and in response, the Klingons have cut off diplomatic relations. Gowron turns up in a ship to invite Worf to the attack on Cardassia. TO BE CONTINUED!