The Enterprise crew alters course to investigate the mystery of Terra Nova, a legendary deep-space Earth colony whose inhabitants mysteriously disappeared decades ago. But when they arrive, they encounter the descendants of the colonists who have become a tribe of human-hating cave-dwellers and more alien than Archer could ever have imagined.

The sudden appearance of a Vulcan starship disrupts Enterprise's probe of an unusual comet containing eisilium, a rare mineral. Trip discovers that T'Pol is transmitting coded messages to the Vulcan ship. After he learns the content of her communiqués, she reluctantly takes Trip into her confidence about her pending marriage on Vulcan. On their mission to the comet for core samples, Reed and Mayweather use explosives that unfortunately shift the comet's rotation. When the sun rises, the ice crumbles and traps them in a crevasse. Captain Archer reluctantly asks the Vulcans for help to use their tractor beam on the shuttle.