A spatial distortion leaves Archer unable to form any new long-term memories. Years in the future, he wakes up one morning and is stunned to learn the outcome of the human-Xindi conflict.

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.

The remnants of an alien ship and two frozen cybernetic bodies are uncovered in the arctic by a research team. These aliens soon thaw out and flee Earth, taking the research team with them. Starfleet orders Enterprise to find them, but the crew aren't prepared for just how dangerous these aliens really are.

Archer sets out on a suicide mission to destroy the Xindi superweapon as Enterprise faces a brutal attack.

With help from Xindi allies, the Enterprise crew attempts to stop the arming of the Weapon aimed toward Earth.

Archer puts his life on the line in a risky gambit to intercept the Xindi superweapon and disarm it from within.

When Trip suffers a catastrophic injury, his only hope for survival is a transplant from a "mimetic symbiont" which Phlox grows from one of his exotic creatures.

An Andorian ship led by Commander Shran arrives in the Delphic Expanse to help Enterprise hone in on the Xindi super-weapon.

Archer and Hoshi stand before the Xindi Council as T'Pol and Reed lead a team into the heart of a Sphere.

Archer, T'Pol and T'Pau attempt to bring the Kir'Shara — an artifact believed to contain Surak's original writings — to the Vulcan capital, as the NX-01 gets involved in a Vulcan-Andorian military clash.

Enterprise journeys to Babel with a Tellarite ambassador on board for peace talks with the Andorians, when a distress call from Shran is received.

Archer tries to unify the Andorians, Tellarites and Vulcans in a plan to capture a marauder ship threatening to destabilize the region.

Starfleet orders Enterprise to return home when the crew seemingly causes the destruction of an alien planet. However, a visit from Crewman Daniels leads Archer to believe that this disaster was the plot of one of the factions from the temporal cold war.

Daniels and Archer must find a way back to the 22nd century in order to make sure history plays out as it should. Meanwhile, on board Enterprise, the Suliban have taken over the ship, but Reed, Trip, and T'Pol formulate a plan to eject the aliens.

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.

Earth's embassy on Vulcan is bombed, and the ensuing investigation puts Archer and T'Pol on the trail of a Vulcan religious faction hiding in a treacherous desert.

Archer visits Shran's icy homeworld to find an Andorian subspecies called the Aenar, to determine their connection to the marauder destroying ships in the region.

In the mirror universe, Commander Archer mutinies against Captain Forrest in order to capture a future Earth ship found in Tholian space.

The Enterprise crew find a small craft drifting in space and are surprised to find it contains a human corpse. More questions arise when the Suliban and Tholians make claims to the craft.

Archer finds himself face-to-face with Degra, the designer of the Xindi superweapon, and tries to get him to reveal its location.

While dissension among Xindi ranks festers, Enterprise tries to recover from a devastating attack.

In the mirror universe, Archer commandeers the 23rd-century Defiant from the Tholians and uses it in a nefarious power grab.

A human isolationist leader threatens to destroy Starfleet Command unless all aliens leave Earth immediately.

Enterprise visits an ancient Vulcan spiritual sanctuary, despite T'Pol's concerns that her human colleagues will be an awkward and disruptive presence there. Upon landing, they discover that the monastery has been forcibly taken over by the Andorians, a paranoid and highly excitable race of aliens with a long history of conflict with the Vulcans.

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.