The crew discovers a new planet with two races, one in desperate need of medical and scientific assistance. In the course of trying to help, Dr. Phlox recalls his own Denobulan past to address the ethical dilemmas that arise in the present.

After Archer and Trip become curious about a visit she made to a Pennsylvania mining town called Carbon Creek, T'Pol explains to them that Vulcans actually had their first contact with humans in 1957. That year, a Vulcan ship crashed on Earth and three crew members survived, including T'Pol's great grandmother. They pose as humans in Carbon Creek and take on jobs while waiting for rescue and soon find themselves becoming more involved with the town's residents.

When attempting to explore a new planet, Enterprise triggers a cloaked mine. While the crew deal with the resulting damage, it's discovered another mine is stuck to the hull. During Reed's attempt to disarm it, a spike is driven into his leg, trapping him out there. While Archer goes out on the hull to help him, the rest of the crew learn they are in a minefield belonging to the Romulan Star Empire, who demand Enterprise leave or face destruction.

Archer and Reed return to a pre-warp society, that is on the verge of war, to recover a lost communicator from an undercover survey mission.

Mayweather discovers his father has died and that things on his old home, the E.C.S. Horizon, have greatly changed.