As Enterprise enters the orbit of Dekendi III, Dr. Phlox prepares to attend the Interspecies Medical Exchange conference. He's also looking forward to being reunited with one of his wives, Feezal, who will be helping Trip install a neutron microscope onboard. Phlox is pleased to see his wife, but the conference raises a troubling issue — Phlox is the only person onboard Enterprise who knows that T'Pol is suffering from Pa'nar Syndrome, an incurable Vulcan disease. He has been able keep the effects of the disease at bay, but he knows that T'Pol will soon need supplemental medications. Otherwise, she might die. The doctor sees the conference as the perfect opportunity to speak with Vulcan physicians, and learn if they have made any headway with the disease. However, he must keep T'Pol's identity a secret, as the High Command cannot learn of her condition.

Unfortunately, the Vulcan doctors — Yuris, Strom and Oratt — see right through Phlox's ruse, and quickly ascertain that T'Pol is suffering from the disease. When Archer learns of this, he is furious and demands to know why Phlox and T'Pol have kept her condition a secret from him. T'Pol explains that Pa'nar Syndrome carries a certain stigma on Vulcan. A small number of Vulcans are born with the ability to form a "mind-meld," and it is through this act that the disease is transmitted. Anyone can be on the receiving end of a meld, however, and T'Pol found herself in that very position when she was attacked by the Vulcan Tolaris the previous year. Because this telepathic minority's behavior is considered "unnatural" on Vulcan, those who carry the disease face prejudice — T'Pol would most likely lose her commission if the High Command were to learn of her condition. Archer urges T'Pol to tell the High Command that she was forced to meld, but she refuses, not wanting to fuel their bigotry.

Later, Dr. Yuris contacts T'Pol and asks her to meet him on the surface. He passes along some research that might help in treating her. T'Pol wonders why he's willing to help her. Yuris explains that he's part of the minority of mind-melders — he does not, however, have the disease. Once he realizes that T'Pol was coerced into melding, he suggests she tell his colleagues, knowing that they will be more sympathetic. She still refuses.

Meanwhile, Trip is dealing with a much less serious problem — Phlox's wife Feezal keeps trying to flirt with him as they work together to install the microscope. Trip is uncomfortable with her advances, and decides to discuss it with Phlox. The doctor, however, does not react as Trip might expect — he enthusiastically suggests that Trip should return Feezal's affections. When Trip points out that Feezal is Phlox's wife, Phlox dismisses him, saying that Trip is too wrapped up in human ideas of morality. Still, Trip is uncomfortable with the situation, and cannot be swayed. Somewhat disappointed, Phlox merely says that it's Trip's loss.

The Vulcan doctors have decided to return T'Pol to Vulcan, where the High Command will determine whether or not she's fit for duty. Archer, however, has discovered a loophole — Vulcan medical protocols entitle T'Pol to a hearing. T'Pol, however, continues to stand by her decision not to explain how she contracted the disease. Archer respects her wishes, but hopes that he will be able to keep her onboard. At the hearing, Archer and T'Pol face the Vulcan doctors, and make points about the Vulcans' narrow-minded attitudes toward mind-melders. Still, it seems to fall upon deaf ears. Then, Dr. Yuris surprises everyone.  Unable to keep silent any longer, he reveals T'Pol's circumstances and informs the other doctors that he is one of the melding minority. Shocked, the doctors allow T'Pol to remain on Enterprise ... but Yuris is suspended and will most likely lose his standing with the Medical Exchange. T'Pol is determined not to let him go down without a fight, however — she plans to contact the High Command. She also hopes that perhaps this incident will encourage others to speak out against the bigotry in Vulcan society.