The second season of Enterprise expanded on the groundwork laid by the show's pivotal premiere year. Characters were given more layers, space was given more dimensions, and foes both new and familiar came into the picture. Here are ten episodes that best demonstrated why the show should have an intriguing future ahead of it.

Carbon Creek
This entertaining outing offers a new take on first contact between humans and Vulcans, but manages to do it in such a way that it works easily enough with established continuity. Jolene Blalock gets a turn in the spotlight, playing both T'Pol and T'Pol's ancestor T'Mir, who crash lands on Earth in 1957. The small town storyline is winning and guest star J. Paul Boehmer stands out as Mestral, a gentle Vulcan who finds reasons to stay on Earth in baseball and I Love Lucy. The twist at the end — is T'Pol spinning a yarn or telling the truth? — enhances the episode's winning charm.

Dead Stop
This episode offers a good old-fashioned horror movie premise —  the highly intelligent space station that masks a deep, dark secret. When Enterprise is need of repairs, it happens to stop off at said station. And while the crew is amazed at all of the amenities the station has to offer, you just know that it's all somehow too good to be true. The sterile design of the station —  which is then juxtaposed with the dark chamber that hides its insidious secret —  is especially neat. And, just when you think everything's tied up in a nice, neat package, we get that classic horror ending, brimming with foreboding.

Stigma
This hour is an example of Trek once again doing what the classic Original Series set out to do metaphorically taking on an important social issue with grace and thought-provoking urgency. Here, we learn that T'Pol has been infected by a deadly Vulcan disease. If she doesn't get more comprehensive medical help, she will die. The disease, however, carries a brutal social stigma on Vulcan, which T'Pol is forced to deal with when some Vulcan doctors learn of her condition. In taking on this moral conundrum, Enterprise shines and T'Pol and Phlox get some nice moments.

Cease Fire
It's always fun to see veteran Trek thesps Jeffrey Combs and Suzie Plakson suiting up in alien make-up. "Cease Fire" offers the unique pleasure of seeing them onscreen together. Both actors do fine work — Combs is cutting but fair as recurring character Shran, while Plakson is quite regal as the rebellious Tarah — and display an adversarial chemistry. The Andorian make-up, meanwhile, is a marvel to behold —  particularly the animated antennae that sit atop the actors' heads, twitching in time with their every mood. Bonus points for good use of the always-welcome Gary Graham as the prickly Soval.

Future Tense
This episode works well as a straight-ahead actioner, but also manages to throw in some nods to the ongoing temporal cold war storyline. After discovering a mysterious vessel from the future, Enterprise gets caught in a crossfire between the Suliban and the Tholians. Both species want the ship and are willing to destroy each other to get it. The effects, it must be said, are amazing, particularly the glorious space battles between the Tholians and the Suliban. The interplay between T'Pol and Archer, meanwhile, adds a nice, character-driven angle —  especially when they are presented with the possibility of humans and Vulcans one day mating.

Horizon
Travis Mayweather hasn't gotten a lot of attention thus far on Enterprise, but this hour demonstrates that he's more than capable of holding his own. "Horizon" focuses tightly on the Mayweather clan, as Travis heads back to his former cargo ship digs for a family visit. The tension between Travis and brother Paul is especially potent and nicely illuminates Travis' main conundrum has he abandoned his family and identity in order to join Starfleet? Anthony Montgomery does nice work with the Mayweather-centric material —  hopefully, he'll be given even more to do next season. Bonus points for the very funny T'Pol-watches-horror-movies sub-plot.

The Breach
Gentle, easy-going Dr. Phlox is usually the character who provides a welcome dose of comic relief, whether he's taking care of one of his many creatures or chatting with T'Pol about the eccentricities of humans. This episode, however, allows John Billingsley to stretch his dramatic wings and adds new shadings to Phlox by introducing a much more serious storyline. "The Breach" has Phlox dealing with a patient who is an Antaran. Because of all the bad blood between the Antarans and the Denobulans, the patient refuses to be treated by Phlox. With this episode, Enterprise takes on an important social issue and gives Phlox some fascinating moral dilemmas. Billingsley carries the hour with grace and assurance.

Cogenitor
This episode looks at the intricacies of human/alien relations pre-Prime Directive with thought-provoking results. When Trip becomes interested in a member of a new species' third gender, he jeopardizes an important first contact. True, Trip acts irrationally here, but there is no denying the appeal of the sexless, subservient Cogenitor, played with remarkable warmth by guest star Becky Wahlstrom. The tragic coda of the episode serves to fully demonstrate the consequences of Trip's actions, and refreshingly, doesn't deliver a too-pat resolution. If anything, it demonstrates that this crew is already facing tough situations with no easy answers — as well as making their share of mistakes.

Regeneration
Another good action-oriented episode, this hour also boasts more meaty parts for the always-entertaining Phlox. Enterprise's run-in with a group of mysterious cybernetic beings (OK, it's the Borg) makes for some fast-paced action scenes, as well as a fascinating prologue involving a doomed research team. The Phlox scenes, though, are what really sing. When Hoshi offers to keep the doctor company, noting that he's taken care of her many times before, it makes for a neat bit of character work that will hopefully be expanded upon in the future.

The Expanse
In the briskly-paced season finale, Enterprise is given a mission with high stakes and long-lasting implications. In a way, this episode is the set-up for what will hopefully become a long-running, multi-layered story arc. If nothing else, "The Expanse" shows promise. As Archer and crew head into the Delphic Expanse, we can only wonder at what they will encounter. That promise of excitement is a tantalizing mystery for viewers to speculate about all summer. Of particular note now that T'Pol has resigned her commission, where does that leave her?