Bashir and O'Brien are in a lab at T'Lani III, trying to destroy Harvesters - a bio-mechanical weapon used by the Kellerun and T'Lani in a recent war. The only difference between the Kellerun and the T'Lani appears to be which silly hairstyle they sport. They succeed in destroying the test batch of harvesters and set about destroying the rest of the stocks.
The pair contact Sisko, who congratulates them, and say they can stay for the night's celebrations. As they're about to destroy the last batch, two Kellerun appear in the lab and start shooting everyone. After overpowering the Kellerun, Bashir and O'Brien find they're unable to escape to the runabout, so they beam down to the planet to escape the battle.
The Kellerun and T'Lani ambassadors report to Sisko that O'Brien and Bashir are dead - O'Brien having tripped a security system which flooded the lab with radiation.
Bashir and O'Brien (I'm going to get tired of typing that) are hiding out in some ruins in military mode. O'Brien thinks they need to hide out until Sisko comes looking for them. They find a comms system which he sets about fixing.
The DS9 command staff reviews the security tape of the incident, which appears to show everyone being vaporised by a radiation pulse. Sisko orders Dax to contact Starfleet to ask for replacements.
Bashir and O'Brien bicker about women. Bashir doesn't think marriage is fair because of the risks of the job. Then he discovers that O'Brien's been infected by Harvesters. Dun dun duuuuuuuun!
Sisko breaks the news to Keiko. Awwwwwww
O'Brien's no longer able to continue working on the coms unit, so Bashir takes over with his instruction.
Dax tells Kira how Bashir let her read his medical school journals. Quark presents them with drinks "on the house", and gives a speech about how good customers Bashir and O'Brien were. Keiko insists that the security records are faked, because O'Brien was drinking coffee in the afternoon. Sisko and Dax decide to go retrieve the runabout from T'Lani III and investigate why the recording's been altered.
Bashir keeps working on the com device and talks about how he had a failed romance with a ballerina. O'Brien can't feel his legs.
Sisko and Dax arrive at T'Lani III and start snooping.
Bashir, meanwhile, has gotten the coms system working, but O'Brien is deteriorating.
Dax reports that someone's tampered with the runabout's log, covering an attempt to remote transport shortly after the time of the supposed accident.
Kellerun and T'Lani find Bashir and O'Brien, and reveal they killed all the scientists because they had knowledge which could allow them to replicate the Harvesters, and now they have to get rid of the pair as well. Fortunately they're beamed out before the soldiers get a chance to fire.
The Kellerum and T'Lani pursue the fleeing runabout, explaining to Sisko that they want Bashir and O'Brien back. They're forced to destroy the runabout, only to find that Sisko and co have escaped on the other runabout.
Back on the station, O'Brien recovers from the deadly superweapon and Bashir gives a speech about how he and O'Brien now have an unbreakable bond. And O'Brien admits he sometimes drinks coffee in the afternoon. Oops.