One of my favorite franchise arcs is the Xindi crisis from Enterprise’s third season, until Discovery and Picard the only example of full serialization in Star Trek.
Of course, as was true of the franchise, to that point, even that left plenty of room for standalone stories, plus a few out-and-out standouts. Here’s a complete rundown:
“The Expanse” - The second season finale kicks off the arc with the Xindi launching an attack on Earth, carving a swatch across Florida and killing, among others, Trip’s sister. The Enterprise is subsequently sent into the eponymous region to seek out the Xindi to confront them and prevent further attacks.
“The Xindi” - We meet the Xindi Council, along with weapons developer Degra, in the third season premiere, but the Enterprise crew itself quickly determines that their search for answers won’t be easy.
“Anomaly” - The region of space they’re forced to travel through is itself dangerous, and contains mysterious spheres, the first of which they encounter here.
“Extinction” - Doesn’t have a ton of arc relevance.
“Rajiin” - Enterprise never understood that modern fans had a hugely different opinion of hot chicks than those of the original series. So this episode, featuring a hot chick helping the Xindi Council spy on the crew, was yet another instance of not getting the expected reception.
“Impulse” The region’s weird properties have negative effects on…everything, but here they’ve resulted in Zombie Vulcans. Fans loved this one. If there was one way to guarantee a good reception, it was to drop in a random horror episode (see also: the second season’s “Dead Stop”).
“Exile” - Sato has another in her long series of uncomfortable situations, this time with an alien who could give them actual information about the Xindi.
“The Shipment” - For me this is the first episode of the season to dig fruitfully into the arc, in which Archer meets some actual Xindi, and discovers that it’s definitely going to only get more complicated.
“Twilight” - One of the true highlights of the arc is also a classic “reset button” episode (in the vein of “City on the Edge of Forever,” “The Inner Light,” “The Visitor,” and “Timeless”) in which a great premise must be undone so there can be a happy ending, in this case Archer losing his ability to retain long term memories and thus seeing an alternate version of how all this plays out, and developing a very different relationship with T’Pol.
“North Star” - A kind of classic original series episode that serves as a kind of metaphor for how the arc will need to play out.
“Similitude” - The other major highlight of the arc sees Trip needing to be saved by growing a clone from which Phlox will harvest needed organs. It’s one of those bitter ethical dilemmas the franchise can do so well, and a great spotlight for the show’s best character.
“Carpenter Street” - The most direct overlap between this arc and the Temporal Cold War, featuring pizza and Jeffrey Dean Morgan nearly quitting acting because of his Xindi getup.
“Chosen Realm” - Another nod to the original series that serves as a cautionary tale for Archer growing too obsessed with the mission.
“Proving Ground” - Our Andorian pal Shran pops up.
“Stratagem” - Another big highlight of the arc is Archer’s considerable battle to win Degra over as an ally. It’s the “In the Pale Moonlight” of the arc, solidifying Degra’s importance and humanizing, once and for all, the enemy, in the best franchise tradition.
“Harbinger” - The crew becomes more aware of the Sphere Builders and their role in all of this.
“Doctor’s Orders” - A Phlox spotlight. Kind of sad, because it forces him to spend a lot of time alone, and he always works best off of other characters.
“Hatchery” - Another cautionary tale of obsession.
“Azati Prime” - The crew reaches the Xindi! But it’s still going to be very far from easy to resolving all this…
“Damage” - Driving home the point that sometimes hard choices must be made.
“The Forgotten” - An episode for grief.
“E2” - The crew interact with their own descendants (like “Children of Time”), and once again the emphasis is on the cost of completing the mission.
“The Council” - Archer, with Degra as his firm ally, meets the Xindi Council. No happy ending here: Degra is murdered by the more belligerent faction of the Xindi as thanks for his efforts.
“Countdown” - Putting all the pieces together, the crew realizes that the Sphere Builders are the ones responsible for all this. But they still have the aggressive Xindi to deal with, and a second assault to stop.
“Zero Hour” - The season finale. You can guess how it ends.
“Storm Front, Parts. 1 & 2” - Well, almost! The fourth season opens by closing out the Temporal Cold War, including recovering Archer from an alternate WWII, where he was whisked at the last minute when stopping the final Xindi weapon.
“Home” - Archer attempts to recover, “Family” style, from the psychological fallout of his traumatic experiences.