Upon returning home after preventing a second Xindi attack, Enterprise explores cultural shifts on Vulcan; forges alliances with Earth's neighbors in the face of Romulan aggression; deals with a plague inside the Klingon Empire; explores the Mirror Universe; and overcomes xenophobic elements to lead an interstellar community.

Season 4 Episode 18 - In a Mirror, Darkly (1)

In the mirror universe, Commander Archer mutinies against Captain Forrest in order to capture a future Earth ship found in Tholian space. Air Date : 22nd-Apr-2005

Season 4 Episode 1 - Storm Front (1)

Archer and the NX-01 find themselves in Earth's past, with events of World War II altered by the Temporal Cold War. Air Date : 8th-Oct-2004  Read More

Season 4 Episode 2 - Storm Front (2)

With Silik's help, Archer hones in on the temporal operative who altered Earth's past and threatens to destroy all of time. Air Date : 15th-Oct-2004  Read More

Season 4 Episode 3 - Home

Once the NX-01 finally returns to Earth, the weary crewmen face repercussions of their journeys, both positive and negative. Air Date : 22nd-Oct-2004  Read More

Season 4 Episode 4 - Borderland (1)

When genetic supermen left over from the Eugenics Wars hijack a Klingon ship, Archer must rely on their creator, the criminal Dr. Arik Soong, to help hunt them down. Air Date : 29th-Oct-2004  Read More

Season 4 Episode 5 - Cold Station 12 (2)

Arik Soong leads his band of Augments to a medical facility where hundreds of genetically enhanced embryos are still stored, intending to retrieve them and bring them to life. Air Date : 5th-Nov-2004  Read More

Season 4 Episode 6 - The Augments (3)

In defiance of their "father," Arik Soong's Augments devise a heinous plot against the Klingons which will surely lead to interstellar war. Air Date : 12th-Nov-2004  Read More

Season 4 Episode 7 - The Forge (1)

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. Air Date : 19th-Nov-2004  Read More

Season 4 Episode 8 - Awakening (2)

Archer and T'Pol encounter the Syrrannites, a radical group hiding in the Vulcan desert, while the NX-01 crew contends with Vulcan power ploys. Air Date : 26th-Nov-2004  Read More

Season 4 Episode 9 - Kir'Shara (3)

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. Air Date : 3rd-Dec-2004  Read More

Season 4 Episode 10 - Daedalus

The inventor of the transporter, Emory Erickson, comes aboard Enterprise for a risky experiment. Air Date : 14th-Jan-2005  Read More

Season 4 Episode 11 - Observer Effect

Non corporeal aliens study the Enterprise crew as they respond to a fatal viral infection brought on board from an away mission. Air Date : 21st-Jan-2005  Read More

Season 4 Episode 12 - Babel One (1)

Enterprise journeys to Babel with a Tellarite ambassador on board for peace talks with the Andorians, when a distress call from Shran is received. Air Date : 28th-Jan-2005  Read More

Season 4 Episode 13 - United (2)

Archer tries to unify the Andorians, Tellarites and Vulcans in a plan to capture a marauder ship threatening to destabilize the region. Air Date : 4th-Feb-2005  Read More

Season 4 Episode 14 - The Aenar (3)

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. Air Date : 11th-Feb-2005  Read More

Season 4 Episode 15 - Affliction (1)

While Enterprise visits Earth for the launch of Columbia, Phlox is kidnapped and forced to help the Klingons deal with a grave threat toward their species. Air Date : 18th-Feb-2005  Read More

Season 4 Episode 16 - Divergence (2)

With Columbia's help, the Enterprise crew grapples with sabotage to their ship as they pursue the truth behind the kidnapping of Phlox. Air Date : 25th-Feb-2005  Read More

Season 4 Episode 17 - Bound

As a gift for negotiating with the Orion Syndicate, Captain Archer receives three Orion Slave Girls. Air Date : 15th-Apr-2005  Read More

Season 4 Episode 18 - In a Mirror, Darkly (1)

In the mirror universe, Commander Archer mutinies against Captain Forrest in order to capture a future Earth ship found in Tholian space. Air Date : 22nd-Apr-2005  Read More

Season 4 Episode 19 - In a Mirror, Darkly (2)

In the mirror universe, Archer commandeers the 23rd-century Defiant from the Tholians and uses it in a nefarious power grab. Air Date : 29th-Apr-2005  Read More

Season 4 Episode 20 - Demons (1)

A xenophobic faction of humanity threatens to undermine talks to form a new coalition of planets. Air Date : 6th-May-2005  Read More

Season 4 Episode 21 - Terra Prime (2)

A human isolationist leader threatens to destroy Starfleet Command unless all aliens leave Earth immediately. Air Date : 13th-May-2005  Read More

Season 4 Episode 22 - These Are the Voyages...

Six years in the future, an emotional Captain Archer and the crew return to Earth to face the decommission of Enterprise and signing of the Federation charter. Air Date : 13th-May-2005  Read More