Trip is alone on a test mission aboard Shuttlepod One, trying out the latest autopilot upgrades. Suddenly, he is fired upon by an alien ship and must make an emergency landing on a nearby moon. It's nighttime, and Trip attempts to repair the transceiver in order to contact Enterprise. While he's working, he is suddenly attacked by a mysterious alien. Trip retreats into his shuttlepod, but quickly notices that the alien interloper has stolen his transceiver.
Meanwhile, Archer has mounted a search for Trip. As Enterprise attempts to track him down, they are hailed by an Arkonian ship and ordered to leave the area immediately. T'Pol warns Archer that the Arkonians are a territorial species, and that Enterprise should proceed with extreme caution. Apparently, relations between the Vulcans and the Arkonians have been contentious for many years. Archer tells the Arkonian captain, Khata'n Zshaar, that he will not leave until his missing crewmember is back onboard. Khata'n Zshaar admits that one of his crew is also missing, and was most likely piloting the alien ship that fired on Trip. Archer proposes that the two crews work together in order to find both missing crewmembers. The Arkonians agree, but T'Pol advises that Archer remain cautious.
Down on the surface, Trip has managed to trick the alien, an Arkonian named Zho'Kaan, into leaving his own campsite so that Trip can retrieve the transceiver. Unfortunately, Zho'Kaan realizes the ruse, and attacks Trip, rendering the chief engineer unconscious. When Trip wakes up, Zho'Kaan demands that Trip fix the alien's transceiver. The repairs are slow-going, as Trip and Zho'Kaan cannot understand each other without the universal translator. They rely on gestures to communicate, however, and eventually learn each other's names. Trip also learns that Zho'Kaan has some unusual abilities. When Trip is injured, Zho'Kaan hisses some strange fluid onto his arm, healing the wound. The two still do not trust each other, however. Frustrated with the alien transceiver, Trip sprays shuttle fluid into Zho'Kaan's face and gains control of the situation.
On Enterprise, the crew works to locate Trip. T'Pol has learned that the moons they are searching experience extreme changes in temperature — in the daytime, the temperature can rise as high as 170 degrees. Alarmed, Archer realizes that they need to find Trip before the sun rises.
With Zho'Kaan as his prisoner, Trip has returned to his spot near the shuttlepod and is attempting to repair his transceiver using some of the alien transceiver's components. After a few attempts, Trip concludes that perhaps he needs to take the transceiver to a higher ground, and asks Zho'Kaan to assist him. But as soon as Trip unties Zho'Kaan, the alien attacks him and the two engage in hand-to-hand combat. Eventually, the pair falls to the ground, exhausted. Too tired to fight, Trip manages to convince Zho'Kaan that they need to work together in order to escape the moon. Together, they take the transceiver to a higher ground and Trip finally manages to make contact with Enterprise.
Unfortunately, dawn is approaching, and as Trip and Zho'Kaan wait for help to arrive, Trip notices that his alien companion doesn't seem to be dealing well with the heat. As Zho'Kaan gets more and more dehydrated, Archer and the Arkonian captain work to lock onto the officers' positions. Archer tells Reed to prepare the transporter, but Phlox advises against it: the Arkonians are extremely sensitive to temperature fluctuations. Thus, Zho'Kaan's dehydration is causing cellular breakdown. Despite Archer's urging, Trip refuses to return without Zho'Kaan — he doesn't want to leave the alien alone. Trip suggests using a modified Arkonian shuttle to rescue the duo, and Archer agrees to look into the possibility. The idea works, and Trip and Zho'Kan are soon on their way back to Enterprise.
Once both officers are onboard and recovering, Khata'n Zshaar bids Archer farewell — he still doesn't seem terribly friendly towards the captain, but T'Pol notes that at least Archer was more successful than the Vulcans in establishing relations with the Arkonians. Meanwhile, Trip visits Zho'Kaan in sickbay, and both men express that they are grateful to have encountered one another.