(Originally published 05.19.04.)

UPDATE: As we head into the Season 4 premiere of Star Trek: Enterprise, by popular demand we are re-publishing this retrospect — which originally ran prior to the season finale "Zero Hour" — of the year-long arc following Jonathan Archer and his NX-01 crew on their treacherous mission into the Delphic Expanse. This is not a complete blow-by-blow of the entire third season, but rather the specific episodes and story points which brought the Xindi storyline to a climax and led into the startling cliffhanger which will be resolved in this week's "Storm Front." Enjoy, and get ready for a dynamite season opener!

The Expanse
An alien probe attacks Earth killing over seven million people.

Enterprise is recalled to Earth. En route, Captain Archer learns from a normally antagonistic temporal operative that the probe was sent by the Xindi, a race determined to destroy Earth with another, more powerful weapon.

Starfleet orders Enterprise to take on a contingent of military personnel — Military Assault Command Operation soldiers, or MACOs — and confront the Xindi in their home region, the Delphic Expanse.

Disobeying orders from the Vulcan High Command, Sub-Commander T'Pol chooses to remain on Enterprise, resigning her commission.

Enterprise then embarks on its mission, entering the Expanse.

The Xindi
Six weeks into the Expanse, the crew encounters a Xindi on a mining planet.

The Xindi-Humanoid reveals that there are multiple species of his people: Xindi-Humanoids (also known as Primates), Xindi-Reptilians, Xindi-Arboreals (or Sloths), Xindi-Insectoids and Xindi-Aquatics.

Before dying, the Xindi gives Archer the coordinates of his homeworld.

Enterprise's progress is being tracked by the Xindi Council.

Enterprise arrives at the coordinates for the Xindi homeworld, finding a debris field and evidence that the planet was obliterated a hundred years prior. The crew continues on in their search for the Xindi diaspora who threaten Earth.

Anomaly
As Enterprise ventures deeper into the Expanse, they encounter destructive spatial anomalies which threaten to destroy the ship with their gravity-distorting power.

The ship is attacked by marauders, and one of the attackers is captured and reveals that the only defense against the anomalies is to insulate the hull with a substance called trellium-D.

The Enterprise crew also discovers a cloaked area of space, and within that a massive, mysterious constructed Sphere, the first of dozens they will discover and chart in the Expanse.

Archer and his crew are able to download a huge portion of a Xindi database from the marauders (who had recently attacked a Xindi ship), expanding their knowledge of the Xindi.

Rajiin
Archer and his crew visit an alien bazaar to obtain the formula for synthesizing trellium-D.

They end up rescuing an alien slave girl named Rajiin.

As Trip and T'Pol attempt to synthesize trellium-D, Rajiin mesmerizes Archer and takes detailed physical scans of him. Rajiin, it turns out, is on a covert mission for the Reptilian and Insectoid Xindi, who forcibly retrieve her from Enterprise.

Other members of the Xindi Council squabble amongst themselves over this dangerous action, but they now have comprehensive physiological information about humans.

Impulse
Enterprise encounters the Seleya, a Vulcan ship adrift in the Expanse, its crew transformed into zombie-like shells of their former, logical selves.

T'Pol begins to be affected by exposure to trellium-D, which Phlox discovers to be a neuro-toxin to Vulcans causing them to lose control of their emotions.

T'Pol's exposure is limited, but the rest of the Vulcans cannot be saved. Unbeknownst to the rest of the crew, this experience will have lasting repercussions for T'Pol.

The Shipment
A tip from an alien the crew encounters leads them to a planet where a substance to be used in the Xindi superweapon is being manufactured.

An encounter with a Xindi-Arboreal named Gralik shows Archer that not all Xindi are the enemy.

Gralik pledges to do what he can to slow the weapon's development, and Archer is able to plant a tracking device on a canister outbound for where the weapon is being assembled.

Carpenter Street
Crewman Daniels, a time-traveling human from the future that Archer has had dealings with before, appears and sends Archer and T'Pol on a mission back in time to Detroit early in the 21st century.

They discover Xindi-Reptilians working on a second plan against humanity, involving a deadly bio-weapon. Archer and T'Pol thwart the plot and return to their own time, with the corpses of the Reptilians and their technology.

Proving Ground
With the aid of an Andorian vessel, Archer is able to covertly observe a test of a prototype of the Xindi superweapon.

The Andorians seize the weapon for their own purposes, but Archer manages to destroy it using intercepted activation codes.

Despite the conflict, the Andorians transmit their detailed scans of the weapon to Archer before they leave.

Stratagem
Using information from the scans the Andorians supplied, the Enterprise crew is able to capture the weapon's creator, a Xindi-Humanoid named Degra.

An elaborate hoax is played on Degra, during which time he reveals the likely location of the weapon — a system known as Azati Prime.

The Xindi scientist's memory of the experience is wiped by Phlox, and Degra is released none the wiser. Enterprise sets course for Azati Prime.

Harbinger
Enterprise makes a strange discovery within an abnormally large spatial distortion — a small craft with an alien inside, hooked up to monitoring equipment.

The location of the craft is equidistant to five of the mysterious spheres which Enterprise has been charting. The alien is dying, as this universe is poisonous to him.

The alien reveals that he is from a trans-dimensional realm, and before he dies, he tells Archer that "when the Xindi destroy Earth, my people will prevail."

Hatchery
Enterprise encounters a damaged Xindi-Insectoid ship and acquires one of their shuttlepods.

Azati Prime
Enterprise reaches Azati Prime and a reconnaissance mission inside the Xindi defense perimeter takes place using the captured Insectoid shuttlepod to scout the superweapon.

Using this information, the crew determines that the weapon can only be destroyed by using the captured pod packed with explosives. Archer decides to embark upon the suicide mission himself. He is suddenly whisked 400 years into the future where Daniels tries to talk him out of it, explaining the entire scenario: The Xindi have been manipulated into their aggression against humanity by the trans-dimensional species who built the Spheres. They wish to reshape the Expanse to make it habitable for themselves and colonize it, but they came to realize that in the future the "Federation" — which Archer will someday be crucial in forming — will fight them and drive them back into their realm. If mankind is destroyed now, the Federation will never exist, and thus the so-called "Sphere-Builders" will prevail.

Daniels urges Archer to find a diplomatic solution, but the captain obstinately proceeds on the suicide mission. However, upon arrival he discovers the weapon has been moved, and he is captured.

While under interrogation by Xindi-Reptilians, Archer makes contact with Degra and manages to instill doubt into the Xindi-Humanoid with the information he just received. Meanwhile, Enterprise is discovered and attacked by Reptilian ships.

Damage
Archer's pleas impact Degra, who orders the attack on Enterprise called off and with the assistance of Xindi-Aquatics, has Archer returned to Enterprise.

T'Pol reveals that she's been secretly self-administering small doses of trellium-D to herself to the point of addiction to the emotional effects of the substance.

The Forgotten
Using all the evidence he has recently acquired, Archer convinces Degra and a Xindi-Arboreal council member that the Sphere-Builders may be manipulating the Xindi into destroying humanity, an act which will lead to the future extinction of the Xindi.

A Xindi-Reptilian vessel discovers the clandestine meeting, forcing Degra to destroy the Reptilian ship. A plan is hatched for Archer to bring his evidence before the Xindi Council.

The Council
Archer presents his evidence to the full Xindi Council. The Humanoids and Arboreals wish to continue the discussion while the Reptilians and Insectoids refuse to consider, let alone believe Archer's evidence.

The Aquatics, the deciding vote on the Council, need more time to evaluate.

The Sphere-Builders, realizing their plan is slipping away from them, convince the Reptilians and Insectoids to move independently. Reptilian commander Dolim kills Degra and seizes control of the superweapon.

Since activation codes from three of the five Xindi species are needed to arm the weapon, the Reptilians kidnap Hoshi Sato, having noted her exceptional linguistic skills, with a plan to coerce her into decrypting the third launch code.

They take Hoshi and the weapon and disappear into a vortex, heading toward Earth.

Countdown
The Xindi Council split, Archer works with the Humanoids and Arboreals to stop the Reptilians and Insectoids. The Aquatics agree to assist Archer if he can disable the Spheres. Meanwhile Hoshi is surgically forced to decrypt the weapon's third arming code.

A massive battle ensues, and Hoshi is rescued, but not before the weapon is fully activated and aimed towards Earth. Since Enterprise doesn't have the speed to catch up with it, Archer's Xindi allies offers him Degra's ship, and he boards it with Reed, a small team of MACOs, and a still-recovering Hoshi. Meanwhile, T'Pol and Tucker stay on Enterprise with a plan to destroy "Sphere 41," in hopes that by doing so they will disable the entire network of spheres, thus keeping Archer's promise to the Aquatics.

Zero Hour
UPDATE: Despite the Sphere-Builders' best attempts to interfere, Enterprise succeeds in destroying Sphere 41, and by doing so disables the entire network of Spheres which has been altering space in the Expanse, thus sealing the defeat of the transdimensional invaders.

Meanwhile, the Xindi Weapon reaches Earth, with Degra's ship in pursuit. With unexpected help from the Andorian Shran, Archer's allies manage to fight the Reptilians and distract them long enough for Archer and his team to transport aboard the Weapon with a plan to overload its power systems. Once nearly completed, Archer orders the other crewmen off the Weapon so he can finish the job by himself. His escape is hindered by Commander Dolim in a last-ditch effort to deploy the Weapon. Archer overcomes the Reptilian and tries to run to the beam-out point, but the Weapon explodes. Earth is saved, but Archer is presumed dead.

The Xindi Council, expressing appreciation for Archer's sacrifice, agrees to reconvene in hopes of patching up the wounds among their people caused by the empty promises of the "Guardians."

An Aquatic vessel transports Enterprise to Earth. When Enterprise attempts to contact Starfleet, there is no response. Commander Tucker and Ensign Mayweather take a shuttlepod toward the surface, and in the air above San Francisco, they are pummeled with bullets from mid-20th-century warplanes.

Meanwhile, a badly burned Archer shows up in a German hospital tent. The Nazi officers wonder about his uniform. Not all of those Nazis are human.