When a Klingon crash lands on Earth following a mysterious incident, Captain Jonathan Archer prepares for the launch of Starfleet's first deep-space starship in a mission to return the Klingon to his homeworld.
As they continue their deep space exploration, the Enterprise crew comes across an alien ship where they discover 15 humanoid corpses that seem to have been part of a scientific experiment. The horrific sight inspires Hoshi to panic and demand a return to Earth, but Archer insists on continuing the mission and finding out more about the abandoned dead. Trouble comes calling when the aliens that were conducting the gruesome experiments return and begin attacking Captain Archer and his team.
When the Enterprise investigates an uninhabited planet that turns out to be far more dangerous than expected. The crew members that visit the planet are infected by an alien pollen that induces hallucinations and paranoia.
When Trip is dispatched to assist an alien ship with its power source problems, he is delighted to have a friendly encounter with one of the ship's female engineers. But after discovering that their special moment has resulted in his becoming pregnant, he realizes he's had an unwitting experience with alien sex. Archer and his crew must then try and return the rapidly growing alien baby to its mother.
The Enterprise crew alters course to investigate the mystery of Terra Nova, a legendary Earth colony whose inhabitants mysteriously disappeared decades ago. But when they arrive, they confront descendents of the colonists who have become more alien than Archer could ever have imagined.
The Enterprise crew pays a friendly visit to 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. Archer soon discovers that the Enterprise crew has gotten in the middle of an interstellar Pandora's Box and now must find a way out.
A Vulcan starship interferes with Archer's probe of an oversized comet.
Captain Archer and the crew discover a fully inhabited, civilized though less advanced Earth-like planet. Disguised to look like its inhabitants, they pay the planet an exploratory visit where they learn that a pernicious illness is afflicting the local population. As Archer seeks to help them find the malady's source, he finds himself in a close encounter with a comely female alien.
The Enterprise crew is dispatched by Starfleet Command to assist Fortunate, a human freight vessel that has been attacked by Nausicaan pirates. On arriving, they are surprised to find that Fortunate's crew is resistant to Archer's efforts to help them and determined to seek revenge against their attackers, no matter what the repercussions.
When the Enterprise comes in contact with an alien vessel transporting stargazers to observe a spectacular stellar event, Archer invites them aboard the ship not realizing that Silik, a Suliban enemy, is among them. Archer quickly realizes that Silik is engaged in a nefarious time-travelling mission and must stop him before he can tamper with the course of history.
When Enterprise is attacked by an unidentified enemy ship, the crew must work frantically to get their new phase canons to operate. Meanwhile, Archer realizes that no one knows Reed well enough to give him a personalized birthday gift.
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.
When Enterprise comes across a wounded Klingon vessel, T'Pol, Hoshi and Reed take a shuttlepod down to investigate. There they are ambushed by a hostile female Klingon who hijacks the shuttlepod, leaving the Enterprise crewmembers dangerously stranded aboard the Klingon vessel. Now it's up to Archer to take the Klingon under guard and enlist her help in rescuing his crew.
Archer and the crew are disappointed to discover that T'Pol has been ordered by the Vulcan High Command to leave Enterprise -and equally frustrated at her seeming indifference to leaving their ranks. T'Pol's last mission as a Starfleet officer, however, proves eventful when she and Archer are kidnapped by a militant faction on an alien planet. However, aid comes to them in the form of the Andorians: their leader, Shran, still owes Archer a debt (from the events of "The Andorian Incident"). It turns out the Vulcans are covertly backing the ruling faction on the planet, while the Andorians are aiding the freedom fighters. With the help of the Andorians, Malcolm and Trip rescue Archer and T'Pol over the objections of the local Vulcan ship, and Shran considers his debt to Archer repaid.
Tucker and Reed set out on a mission in a shuttlepod, as Enterprise is busy investigating an asteroid field. Disaster strikes while the pair are away, leaving the shuttlepod damaged and the warp drive inoperable. They manage to make it back to the rendezvous coordinates only to discover Enterprise was apparently destroyed when it crashed into an asteroid. With the ship seemingly no more, the pair are left abandoned in the middle of nowhere with only a few days of air remaining.
The Enterprise encounters a group of Vulcan civilians who have split off from the normal way of Vulcan life in an effort to explore their emotions. T'Pol is disturbed by the new visitors and warns the Captain that all attempts in the past to integrate Vulcan emotions into their lives has proven disasterous. Meanwhile a message from Admiral Forrest leaves the Captain with the difficult task of trying to convince one of the visiting Vulcans to call home to speak with his dying father.
While exploring an uncharted planet, Enterprise crew members encounter a group of aliens who are hunting down indigenous creatures for recreation. During their exploration, Archer is mesmerized by visions of a woman desperately attempting to communicate with him. The woman's ethereal distress signal informs Archer that she and others like her are actually the prey of the alien hunters. Heeding her call, Archer levels the playing field against the alien hunters.
The Enterprise encounters Ferengi pirates who use gas to knock out the crew and look for treasures on the Enterprise. But they haven't counted on Tucker, who happens to be in the decon chamber and avoids the gas, and attempts to win back the ship from the pirates.
While exploring a crashed vessel on a desolate planet, the Enterprise crew is haunted by some ghostly figures, and they encounter an alien race that has survived despite insurmountable odds. Trip helps repair their derelict vessel and is befriended by Liana, an attractive humanoid alien who develops feelings for him.
While exploring a planet, Archer and Mayweather enter a "military zone" and are detained in an internment prison by an alien race called Tandarans, who are at war with the Suliban. While the Enterprise crew's previous encounters with the Suliban have been disastrous, Archer and Mayweather find themselves sharing a cell with some Suliban detainees who they believe may be wrongly imprisoned.
A strange, symbiotic alien creature boards the Enterprise capturing a few of the crew members, including Archer and Trip, and cocoons them in its web feeding off their bodies to survive. With the captured crewmembers' lives in jeopardy, Hoshi, under T'Pol's command, faces her biggest challenge by trying to find a way to communicate with the lifeform in order to return it to its home planet.
The Enterprise is sent to the planet Mazar to pick up a Vulcan ambassador expelled for misconduct.
When Archer and Trip are invited to a desert-like planet by an alien leader, after they help fix his ship, discover he is a terrorist who has lured them onto his planet under false pretenses. Meanwhile, T'Pol, while in command, faces a tough decision when she cannot locate Archer and Trip in the desert.
When the crew takes shore leave on the famous pleasure planet of Risa, Archer has a mysterious encounter with an alien woman; Hoshi has a surprising romantic rendezvous; Mayweather has a rock-climbing accident; and Trip and Reed go clubbing only to end the evening as unwitting victims of robbery. Meanwhile, Phlox stays on board the Enterprise with T'Pol to take his annual 48-hour hibernation and exhibits some uncharacteristic oddities when they have to wake him up after an injured crew member returns from shore leave.
Starfleet orders Enterprise to return home when the crew seemingly causes the destruction of an alien planet they were exploring. Archer is visited by former crew member Daniels, who traveled through time to warn him that the Suliban are trying to sabotage Enterprise's mission, and the two travel through time to try to thwart the Suliban's plans.
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.
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.
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.
Archer spends a night in sickbay with Dr. Phlox after Porthos contracts a deadly virus on the Kreetassan homeworld. Crew members suspect Archer's increased stress level is due to Porthos' illness, but Dr. Phlox suspects it has to do with Archer's repressed sexual tension.
In need of fuel, the Enterprise arrives at a Quonset mining colony for deuterium supplies. They discover that Klingons are forcing the colonists to give up all their deuterium. Archer and the rest of the crew work to train the colonists so they can fight back against the Klingons.
Archer, Mayweather and T'Pol travel to an arctic world to apprehend a fugitive, when T'Pol is contacted by Vulcan High Command. The mission takes a dangerous turn when T'Pol begins having flashbacks that suggest the events she remembers about a former mission may not accurately relate to what happened.
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.
While Enterprise is surveying a black hole in a trinary star system, the stellar phenomenon causes strange effects on the crew.
Hoshi experiences her first transporter experience and strange aftereffects lead her to believe she wasn't reassembled correctly.
Trip boards an alien cargo vessel to help repair a stasis pod, which holds a beautiful woman in suspended animation. When the woman accidentally wakes up, she reveals she's not a passenger, but a prisoner.
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.
During a solo test mission on Shuttlepod One, Trip is attacked by a territorial alien and forced to land on the night side of a moon. As he tries contacting Enterprise, he discovers his alien foe has made an emergency landing nearby. The two contend with each other as an extremely hot sun rises and threatens both their lives.
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.
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.
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 and Tucker are arrested and placed on a prisoner transport heading for a penal colony, Canamar. They won't have a chance to correct this error as one of the inmates plots a takeover of the ship.
Noncorporeal aliens possess the bodies of the Enterprise crew.
In a Klingon tribunal, Archer stands accused of aiding fugitives of the Empire and faces death if found guilty.
Mayweather discovers his father has died and that things on his old home, the E.C.S. Horizon, have greatly changed.
When militants take over a world, the Enterprise crew move to evacuate Denobulan geologists that are deep underground. Meanwhile, Phlox has to save a dying Antaran that refuses treatment due to the history of their races.
The Enterprise crew makes first contact with the Vissians, a species with three genders. Trip meets one of the species' third gender, known as Cogenitor, and learns how badly Vissians treat all Cogenitors. Trip attempts to help the Cogenitor, even though it interferes with Vissian culture.
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 tells T'Pol the story of when he and a rival named A.G. Robinson were in competition for breaking the Warp 2 barrier.
Archer learns the Klingons have put a price on his head when he is captured by a Tellarite bounty hunter. As Enterprise pursues, a virus causes T'Pol to go into premature Pon Farr.
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.
Captain Archer and his crew set out to gain information about the mysterious and antagonistic Xindi race.
Enterprise starts experiencing effects of the spatial distortions pervading the Delphic Expanse, and falls victim to predatory aliens.
On a mission to investigate an abandoned Xindi vessel on a jungle planet, Archer, Reed and Hoshi succumb to a virus that mutates them into a primal life form.
The NX-01 gets closer to a showdown with the Xindi when Captain Archer takes on an enigmatic passenger: a beautiful slave named Rajiin.
When Enterprise responds to a distress call from a Vulcan ship stranded in the Delphic Expanse, Archer and his boarding team are attacked by insane zombie-like Vulcans.
A powerful telepath makes contact with Hoshi and offers to help Enterprise find the Xindi ... for a price.
Archer, Reed and Major Hayes infiltrate a Xindi-Sloth industrial colony to learn more about the weapon of mass destruction that will be used against Earth.
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.
When a settlement of humans living a 19th-century Western lifestyle is discovered on a Delphic Expanse planet, Archer and crew set out to learn how they got there.
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.
Archer and T'Pol travel back in time to 2004 Detroit to stop a Xindi plot.
Religious zealots hijack Enterprise to use it as a weapon against the enemies of their faith.
An Andorian ship led by Commander Shran arrives in the Delphic Expanse to help Enterprise hone in on the Xindi super-weapon.
Archer finds himself face-to-face with Degra, the designer of the Xindi superweapon, and tries to get him to reveal its location.
As Archer tries to unravel the mystery of a rescued alien, long-simmering feelings explode among his senior officers.
The fate of Enterprise is in Dr. Phlox's hands as the rest of the crew must be induced into a coma in order to survive a trans-dimensional disturbance.
Archer goes to extreme lengths to save an abandoned nest of Xindi-Insectoid eggs ready to hatch.
Archer sets out on a suicide mission to destroy the Xindi superweapon as Enterprise faces a brutal attack.
While dissension among Xindi ranks festers, Enterprise tries to recover from a devastating attack.
Two high-ranking Xindi offer to stop the launch of their superweapon if Archer can prove they've been manipulated. Meanwhile, the crew mourns their lost mates.
An attempt to use a Xindi subspace corridor leads the Enterprise crew to a bizarre encounter with their own descendants.
Archer and Hoshi stand before the Xindi Council as T'Pol and Reed lead a team into the heart of a Sphere.
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.
Archer and the NX-01 find themselves in Earth's past, with events of World War II altered by the Temporal Cold War.
With Silik's help, Archer hones in on the temporal operative who altered Earth's past and threatens to destroy all of time.
Once the NX-01 finally returns to Earth, the weary crewmen face repercussions of their journeys, both positive and negative.
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.
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.
In defiance of their "father," Arik Soong's Augments devise a heinous plot against the Klingons which will surely lead to interstellar war.
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 and T'Pol encounter the Syrrannites, a radical group hiding in the Vulcan desert, while the NX-01 crew contends with Vulcan power ploys.
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.
The inventor of the transporter, Emory Erickson, comes aboard Enterprise for a risky experiment.
Non corporeal aliens study the Enterprise crew as they respond to a fatal viral infection brought on board from an away mission.
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.
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.
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.
With Columbia's help, the Enterprise crew grapples with sabotage to their ship as they pursue the truth behind the kidnapping of Phlox.
As a gift for negotiating with the Orion Syndicate, Captain Archer receives three Orion Slave Girls.
In the mirror universe, Commander Archer mutinies against Captain Forrest in order to capture a future Earth ship found in Tholian space.
In the mirror universe, Archer commandeers the 23rd-century Defiant from the Tholians and uses it in a nefarious power grab.
A xenophobic faction of humanity threatens to undermine talks to form a new coalition of planets.
A human isolationist leader threatens to destroy Starfleet Command unless all aliens leave Earth immediately.
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.
