Preparing for an Away Team mission to a planet with a large reserve of gallicite, Torres is taken aback when a Vulcan ensign named Vorik asks her to be his mate. She declines, but Vorik grabs hold of her face and she dislocates his jaw. The Doctor explains that Vorik is going through a Vulcan mating ritual known as the pon farr. If he doesn't mate, he may die. Vorik attempts to get through the difficult period by engaging in intensive meditation.
The Away Team begins the search for the gallicite, but Torres is strangely aggressive, at one point viciously biting Paris. Tuvok finds out that Vorik touched Torres' face, which initiated a telepathic mating bond between them. Now Torres is also experiencing pon farr. Vorik is half-mad with his desire to mate with Torres, but he's forced to remain on Voyager, where the Doctor tries to help him by programming a holographic Vulcan female.
Back on the planet, Paris, Tuvok and Chakotay locate Torres and explain to her what she's experiencing. As they try to convince her to leave the planet, a group of subterranean aliens surround the Away Team. A scuffle breaks out and the aliens disappear with Chakotay and Tuvok, leaving Paris and Torres alone. While searching for their missing crewmembers, Torres alludes to the idea of Paris mating with her, but he refuses to take advantage of her.
Chakotay and Tuvok convince their alien captors, the Sakari, that they've come in peace. The Sakari explain that they moved underground after their ancestors were attacked by unknown invaders. Chakotay offers to help them protect themselves from future attacks in exchange for some gallicite. Elsewhere, Torres tries to seduce Paris, but he again rejects her advances. Not long after, Tuvok and Chakotay locate the pair.
Suddenly, they're joined by Vorik, who can no longer resist his instincts. He challenges Paris for Torres, but Torres takes up the challenge herself and engages in the ritual battle, overcoming Vorik. The blood fever purged, the Away Team returns to the ship — but not before Chakotay finds evidence of who the invaders were that attacked the Sakari: the Borg!