Bashir doesn't appreciate Cardassian literature. Garek looks ill, but refuses treatment.
Also, Dax's ugly plant is sick. Bashir says he's a doctor, not a botonist, but they work out there's a fungus which it needs and end up chatting about Garek instead. Later on, Bashir spots the Cardassian making deals with Quark. He unsuccessfully asks O'Brien about recovering Cardassian medical files from the computers, and then is called to Quark's, where Garek is sloshed. After a struggle with the bottle, Garek collapses and Bashir has him beamed to the infirmary.
After some scans, Bashir finds that Garek has a brain implant. Mmmm, braaaaains. Odo suggests it might explain why Quark's been making secret calls to Cardassia. Unfortunately the Cardassian he contacts discovers that the request code is classified, and he's about to be visited by the Obsidian Order, the Cardassian secret police.
Meanwhile, Garek has checked out, so Bashir goes to his quarters and finds him injecting himself with anesthesia. He reveals that it's a safeguard in case he's captured and interrogated for the information he has - it stimulates the pleasure centres of his brain. Problem is, life on the station for him is torture, so he worked out a way to turn it on manually. Two years of use, and it's breaking down. Since he's now dependent on the device, he doesn't feel that turning it off is an option. He also tells a charming story about how he once destroyed a shuttle with Bajoran refugees trying to flee Bajor during the occupation.
Bashir convinces him that turning off the chip's the only course of action, and so Garek's taken to sick bay where he has terrible withdrawal symptoms and admits he actually let the shuttle go. Puzzled by the fact Garek isn't getting better, Bashir rechecks the samples and finds that Garek's biology has changed and he needs... medically stuff. Garek trots out another tale about how he tried to betray his best friend, but his best friend betrayed him first. Cardassians are a lovely bunch, aren't they? Bashir isn't really following all this (Not surprised) and decides to go locate Garek's friend.
Bashir talks to a Cardassian who says that he's been sent on a wild goose chase. Disappointed, he returns to the station, where Garek is recovered and denies being a member of the Obsidian order. Our moral for the day: All Cardassians are dicks.