On the Bridge, a planet appears on sensors, adrift and without a solar system. Captain Archer orders the ship to investigate, and T'Pol scans the planet. Lt. Reed detects a ship near the equator, and when it doesn't respond to Ensign Sato's hails, Archer, T'Pol, Reed and Hoshi Sato take a shuttlepod down to the surface. The away-team find the remains of a campsite 200 meters from the alien shuttle. T'Pol and Reed return to the shuttle while Archer and Hoshi stay. As they walk through the jungle, they are surprised by two Eska. Both parties return to the camp, where they find Archer and Hoshi with another Eska called Damrus.
The Eska call the planet Dekala and they allow the away-team to spend the night. Over dinner, Damrus explains that the Eska have been visiting Dekala for nine generations to hunt the wildlife. As the away-team turn in for the night, Archer hears a woman's voice calling his name. Archer leaves the camp and finds a blonde woman in a clearing, who runs away. Later, none of the Eska nor the away-team report seeing anything unusual, and the Enterprise reports no other ships in orbit or on the surface.
In the morning T'Pol goes to investigate a geothermal shaft. Archer sees the woman again and follows her. She tells Archer in English that he is different from the others and then looks distressed, exclaiming "Harm!" and then disappears. Meanwhile, Damrus and Burzaan detect a Wraith which attacks Burzaan. Archer has Burzaan sent back to the Enterprise for treatment, and insists on going to find the woman again. In Sickbay, Dr. Phlox reports that he has found cellular residue in Burzaan's wound. By the steam vents, Archer encounters the woman again. She says that her kind can assume the form of anything on the planet, and that her kind are the most-prized prey for the Eska. The Wraiths want the hunting to stop.
Later, the Eska and the away-team are gathered around the camp-fire. When questioned, Damrus explains that the reason they visit Dekala is because the prey can sense their thoughts, making them challenging to hunt and kill. Back on board the Enterprise, Archer asks Phlox if he can find a way for the wraiths to mask their chemical signature. In the Mess Hall, Archer tells Trip about a poem by William Butler Yeats, The Song of Wandering Aengus. The form taken by the Wraith is the same as the woman imagined by a young Jonathan Archer when he listened to the poem. On Dekala, the hunting-party are now having problems detecting the wraiths. Damrus wonders why, and Archer blames it on bad luck. The Eska depart and Archer encounters the woman for the final time. As she moves off into the forest, the Wraith assumes its natural form, a large gastropod.