The quartet of genetically engineered individuals from the episode "Statistical Probabilities" show up on the station, impersonating an Admiral and his staff. They help Julian Bashir refine a medical instrument so he can operate on Sarina Douglas.
The operation is a success and Sarina is able to speak for the first time in a long time, even going so far as to notice "everything." When she's reintroduced to the rest of her group, they immediately try to help her feel included by starting up a sing-a-long. Though initially only able to sing in monotone, within minutes Sarina masters solfège and is able to improvise a round with the others.
The quartet later is discussing the eventual collapse of the universe, trying to figure out how to stop it. When Sarina argues against the feasibility of doing so, Jack shuts her down. When Bashir comes in to check on her later, she's seated drawn within herself as she was before the operation was a success, and, fearing the worst, he goes over to check on her. However, she had resumed this stance to stay out of the discussion because she had been made to feel her participation in it was unwelcome.
Bashir falls in love with her and assigns another doctor to take over her care so he can pursue her romantically. Miles O'Brien expresses his concerns to Julian. Indeed, Sarina is not ready for a relationship but feels pressured to thank Julian by being the woman of his dreams. At the end, she leaves DS9 for a scientific internship.