En route to exploring the Arachnid Nebula, the crew of Enterprise NX-01 is hailed by a civilian Vulcan ship. The ship's captain, Tavin, reveals that his vessel is in need of repairs. Archer offers to help, provided the Vulcans don't mind tagging along for the exploration of the nebula. While the Vulcan engineer, Kov, and Commander Tucker work together to repair the ship, Archer and T'Pol host Tavin and one of his crew, Tolaris, for dinner. Over the course of the meal, Archer and T'Pol are shocked at the emotionally pleasant and open nature of their guests. Tavin explains that he and his crew are referred to as "V'tosh ka'tur" ("Vulcans without logic") by the Vulcan elders. He clarifies that they are on a pilgrimage to explore and incorporate their emotions, to find a balance between emotion and logic.
After dinner, Archer discusses the visitors with T'Pol, wondering why she seems to be avoiding them. T'Pol confesses that she is skeptical of Tavin's quest, saying that attempting to re-integrate emotions into the Vulcan psyche is dangerous. Archer disagrees, and gently suggests that perhaps T'Pol should spend more time with her brethren before she judges them. Later that night, T'Pol encounters Tolaris in the Mess Hall. She is surprised to find that he displays formidable intelligence, presenting convincing arguments for his experiments with emotion. The next day, T'Pol and Tolaris work together in the Vulcan Astrometrics Lab, studying the nebula. Tolaris continues to explain his ideas behind re-integrating emotions, and, basing it as a scientific experiment, suggests T'Pol forego her nightly meditation. Her dreams, he insists, will be much more interesting. That night, T'Pol takes Tolaris' advice and does not meditate before bed. As Tolaris predicted, her dreams are quite interesting ... and provocative. In fact, T'Pol's sensual dream involves none other than Tolaris himself! Disturbed, T'Pol pays a visit to Dr. Phlox, who gives her a minor injection and advises her not to give up on Tolaris' techniques — but perhaps she should take things a bit more slowly.
As T'Pol attempts to deal with her emerging emotions, Archer receives a transmission from Admiral Forrest, informing him that Kov's estranged father is dying, and wishes to make peace with his son. Archer approaches Kov about the matter, but Kov is reluctant to speak with the father. Knowing that Trip and Kov have become close, Archer enlists his chief engineer to convince Kov of the importance of the matter. Kov appreciates their efforts, but insists that he and his father said good-bye a long time ago.
Meanwhile, Tolaris convinces T'Pol to allow him to guide her through her emotional awakening. Later, in T'Pol's quarters, he explains that he will use a "mind meld," an ancient technique that will allow the two Vulcans to share their thoughts and memories. As Tolaris places his hands on her face, T'Pol finds herself settling back into her dream from the night before. As T'Pol's emotions swell, she reaches an uncomfortable point and wishes to end the mind meld. Tolaris refuses, and gets angry when T'Pol tries to break the meld. T'Pol is finally forced to violently tear herself away from him, leaving them both heavily stunned from the mental trauma. Desperately trying to control her feelings of mental violation, T'Pol forces Tolaris to leave.
The next day, Archer confronts Tolaris about assaulting T'Pol. Tolaris tries to dismiss the matter, saying that T'Pol simply panicked during their mind meld. Eventually, Archer goads Tolaris into losing control — the enraged Vulcan throws Archer across the room. Having proven that Tolaris is a dangerous man, Archer firmly suggests that the Vulcans take their leave of Enterprise. Before they set off, however, Kov reveals that, thanks to Trip's persistence, he has contacted his father. As the Vulcans leave Enterprise, Archer pays the recuperating T'Pol a visit in her quarters. The Sub-commander has returned to her meditating — she feels that she will eventually recover, but confesses that she envies the human ability to dream.