The infinite blackness of space is interrupted for the Enterprise crew by the discovery of a beautiful new world a natural Eden of unexplored mountains, rivers, wildflower fields and forests. Dismissing T'Pol's cautious advice to conduct scans and tests from orbit before commencing any surface exploration, Captain Archer orders an away team and shuttlepod prepped. Joining Archer on the team are Crewmen Cutler, an entomologist, and Novakovich, a botanist, along with Commander Tucker, Ensign Mayweather, and T'Pol. Even Porthos, Archer's dog, comes along for the ride. The landing party takes in the fresh air of the virgin world before splitting up to pursue their specialties and enjoying a day of exploration amidst uncountable new species of exotic plant and animal life. At day's end, T'Pol, Cutler and Novakovich request permission to stay overnight to study nocturnal life, while Tucker and Mayweather ask to stay for the sheer fun of camping under the stars.
After a relaxing evening of stargazing and ghost stories around a fire, the campers retire to their tents, but are unable to sleep as a sudden and fierce windstorm envelops them. Retreating to the safety of a nearby cavern, the decision is made to wait out the storm before attempting a risky shuttlepod landing, and the crew settles in. Noticing the food packs were left behind, Mayweather volunteers to go back and retrieve them. Pounded by vicious winds and intense darkness at the campsite, Mayweather sees three looming humanoid figures in the shadows, and double-times it back to the safety of the cave. As T'Pol uses her scanner to confirm there are no lifesigns in the vicinity, suggesting Mayweather imagined the figures, Novakovich hears strange alien whispering coming from the tunnels at the back of the cavern. As his fear and panic build, Novakovich is unwilling to stay in the cave only to wait and be attacked, and runs wildly out into the storming darkness. Following behind, Tucker and Mayweather are unable to locate the inexplicably irrational Novakovich, and during their search they see alien faces and bodily movements from within the very rocks and cliffs themselves, before being forced to turn back by the dangerous storm. Archer communicates to Tucker that he and Lt. Reed are coming to the surface in a shuttlepod to attempt a rescue. T'Pol uses the time to explore deeper into the tunnels with her scanner, attempting to verify the alien voices Novakovich heard earlier. Her fear escalating, Cutler is unwilling to be alone and follows after T'Pol, only to imperceptibly observe a meeting between T'Pol and two unknown alien figures.
Once the group rendezvous back in the cavern, the mood is extremely anxious and tense as Tucker and Mayweather describe their alien sightings. T'Pol reports no lifesigns within the tunnel systems, but Cutler accuses her of lying, describing the meeting she observed between T'Pol and the unidentified aliens, which T'Pol denies. Tucker supports Mayweather and Cutler, as he himself saw the alien rock-creatures, and suspicions run high as T'Pol is confronted by the rest of the team. Archer and Reed arrive, but unfortunately are unable to land the shuttlepod in the extreme winds, forced to leave the crew to wait out the storm in the cavern. Onboard Enterprise, Ensign Sato reports that Novakovich's bio-signs are erratic, and Archer hears the crewman screaming incoherently, so he orders Reed to attempt a risky bio-transport. Novakovich materializes onboard Enterprise, but rock and twig debris from the storm have fused into his body. The crewman is treated and stabilized by Dr. Phlox, who discovers that his bloodstream is filled with a potent psychotropic compound called tropolisine. Apparently he contracted the hallucinogen from the local pollen that was kicked up by the winds.
Trying to communicate this discovery to T'Pol, Archer finds out that Tucker is pointing a phase pistol at T'Pol for suspicion of treason. Tucker is extremely volatile as he states to Archer that he always knew T'Pol was there to sabotage Enterprise. Archer orders Tucker to lower the phaser, explaining that the "aliens" were hallucinations caused by the pollen. Though highly skeptical, Tucker begrudgingly follows the order, but he continues to vehemently accuse T'Pol of conspiring with the hidden aliens, while Mayweather and Cutler pass out. Meanwhile Dr. Phlox reports to Archer an unexpected complication: this specific form of tropolisine breaks down into a deadly toxin within the bloodstream, and it may be too late to save Novakovich. But there may be time for the crew on the surface, so Archer explains to Tucker and T'Pol that Phlox is preparing ampules of inaprovaline that will be transported down for them to inoculate themselves. But Tucker is more violently paranoid than ever and on the verge of shooting T'Pol. While Sato and T'Pol converse in Vulcan, Archer plays into Tucker's delusions and "admits" that T'Pol was meeting with the "rock people" for a top-secret mission, tricking him into lowering his weapon. T'Pol immediately stuns Tucker with her own phase pistol, then collects the medication and inoculates herself and the unconscious crew.
The morning brings sunshine and a gentle breeze, leaving the delusions and paranoia behind. A regretful Tucker admits to T'Pol that he needs to challenge his preconceptions about Vulcans. After learning that Novakovich is going to be fine, the stranded crewmembers gather their gear and help each other through the beautiful morning toward an awaiting shuttlepod.