An alien race known as the Xindi launch an attack on Earth, causing great casualties and massive damage. As Enterprise heads back home, an unlikely source informs Archer about the Xindi and that their next attack will destroy Earth.
Travis's visit home to the ECS Horizon becomes rather turbulent, as he clashes with his brother, the ship's new captain, and as the ship is attacked by pirates.
Archer and Trip are wrongly arrested and placed on a prisoner transport heading for a penal colony named Canamar. Things go from bad to worse when one of other prisoners plots a takeover of the ship.
The Enterprise crew find a small craft drifting in space and are surprised to find it contains a human corpse. More questions arise when both the Suliban and Tholians make claims to the craft.
Both the Vulcans and the Andorians make a claim to a small planet and military conflict soon erupts. As the fighting goes on, the Vulcans announce they are willing to discuss cease fire terms. However, Imperial Guard officer Shran believes only Captain Archer can be trusted to mediate the situation, which drags the Enterprise crew into the tense situation.moreless
Enterprise visits a planet where an Interspecies Medical Exchange conference is being held. Dr. Phlox tries to obtain research on a terminal disease from the Vulcan contingency, without revealing T'Pol has been infected by it.
When a lethal neutronic storm approaches faster than Enterprise can escape, the crew take shelter in the maintenance shafts inside the warp nacelles. They also provide refuge to a group of aliens, who aren't exactly honest about themselves.
After T'Pol is contacted by the Vulcan High Command, Archer, Mayweather and T'Pol travel to an arctic world to apprehend a fugitive. The mission takes a dangerous turn when T'Pol begins to have flashbacks that suggest the events she remembers about a former mission may not accurately relate to what happened.moreless
In need of fuel, Enterprise visits a mining colony for deuterium supplies. The crew discovers that the colony is being controlled by Klingon marauders who are regularly pillaging the mined deuterium.
Archer spends a night in sickbay after Porthos falls ill with a deadly virus following a visit to an alien planet.
Suffering from damage inflicted in the Romulan minefield and unable to complete repairs on their own, Archer orders a distress call to be put out. A response leads Enterprise to a repair station, which surprisingly has no crew aboard it and is run by computer. Repairs on Enterprise are carried out quite efficiently and quickly, though the price for all this is much higher than the crew could've guessed.moreless
Whilst attempting to explore a new planet, Enterprise triggers a cloaked mine. While the crew deal with the resulting damage, it's discovered that 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.moreless
After Archer and Trip become curious about a visit T'Pol made to a Pennsylvanian mining town called Carbon Creek, she tells the two a tale about a Vulcan ship that crash-landed in 1957.