O'Brien is trying to unseal an airlock to get some people out, when he's bitched at by a visiting starship captain cause his ship hasn't been fixed yet. Then Dax calls him over cause her office is making loud noises. After he fixes a replicator, the camera pans down to show some flashing device hidden in the works...
Meanwhile, Odo and Quark are exchanging pleasantries and being shouted at by his customers who attempts to make Quark eat his own food until Odo kicks him out. Quark is annoyed because O'Brien hasn't fixed his replicators yet, and overrides the computer so he can locate the working replicators on the command decks. Dax and Kira find him celebrating his repaired replicators.
O'Brien starts speaking nonsense. Different to the normal technobabble, that is. Bashir can't find anything wrong, but O'Brien's incapable is communicating. Then while discussing the problem, Dax develops the same problem, and other crew members begin developing aphasia too. Sisko quarantines the station. Today appears to be freaky virus day on Star Trek (though sadly the TOS episode was just the one with Zephram Cochrane and not a freaky virus episode).
Odo catches Quark raiding the replicators in the command quarters. Bloody Ferengi. Of course, this is the cue for Bashir to reveal the virus is coming from the command quarters replicators. It has also mutated into an airborne virus, so everyone is royally screwed. Or hatstand pyjamas, as they'd put it.
Kira locates the device screwing up the replicators, which she says is Cardassian. Sisko finds Quark trying to extract money from the stricken patients for past debts. Bloody Ferengi.
Bashir establishes that the device screwing up the food was actually a Bajoran device, and Sisko sets Kira to work finding out who in the Bajoran resistance planet the device. O'Brien gets sicker and feverish.
Bashir develops aphasia and is no longer able to communicate with the computer to develop a cure. Kira locates a scientist who might have had something to do with the virus, and sets out in a runabout. Then there's more fun as one of the visiting captains tries to break his ship free of the station, damaging his ship and introducing the danger of imminent explosion.
Kira beams up the scientist and brings him back to DS9, where Odo and Quark are in charge because everyone else is aphasic. The scientist sets to work on an antidote, while Odo deals with the imminently exploding ship. Everyone is cured. Teh end.
That was amusing! Although I've already had enough Odo/Quark banter. Or enough of Quark, for that matter. *is distracted by Batman*