In brief: Pleasant but too familiar.
Part of me enjoyed the easygoing dialog and sensibilities of "Oasis," which is for the most part a quiet, well-acted outing that scores lots of points for being amicable. But then logic takes over where emotions taper off, and I see before me a story that is very obviously derivative and predictable — a Trek story that borrows generously from Trek stories that came before.
The cynic in me that wants to say "been here, done this" is beaten into quasi-acceptance by the sentimental optimist, who notes that even if this story isn't new, some of it works on an emotional plane. Which side of me wins this debate? Neither, because "Oasis" is quite simply too average for either side to get worked up about.
Probably not very useful is the episode's idea of playing much of the show as a mystery, particularly given how painfully conventional the solution ends up being. In this day and age, where major story twists are benchmarked by those found in movies like, say, The Sixth Sense or Fight Club, "Oasis" finds little of value when playing the mystery card.
The mystery is the question of a marooned crew on a crashed vessel. Before visiting this crew, Archer is handed an ominous warning by a passing trader (Tom Bergeron) who recently came in contact with them: "The, um ... crew objected," he says, before adding, mysteriously, "There wasn't anything alive."
The Enterprise away team lands on the planet to find what initially appears to be a deserted ship, before finding the crew hiding out in a room that apparently protects them from being detected by sensor sweeps. This crew says they've been stranded here for three years after crashing, unable to repair their ship. Archer offers to help, and in the process of making repairs, Trip and T'Pol come across some strange facts that indicate this crew isn't being completely forthcoming about their situation, hence the episode's air of mystery: What is this crew hiding and why? The big "shocker" comes in the form of a long-dead corpse in an escape pod orbiting the planet. It's the corpse of one of the crew members Trip has seen alive and well on the planet surface. How can that be? Are they ghosts? (Cue ominous music.)
The answer is predictable, conventional, and familiar: The crew is made up of holograms, save two survivors: Ezral (Rene Auberjonois) and his daughter Liana (Annie Werscing, whose character sometimes bears an uncanny resemblance to Kes from the early seasons of Voyager). They alone survived the crash some 20-plus years ago, when Liana was still a very young child. Ezral, unable to repair the ship to leave the planet, designed the holographic crew to become her — and his — extended family. Similar plots/themes include DS9's comparable "Shadowplay" and TNG's superior "The Survivors."
That's about all there is to the less-than-surprising plot, but what I liked about this episode was its presentation. Trip and Liana strike up a sweet, understated chemistry that reveals Trip as quite the gentleman. Such a gentleman, in fact, that I wanted to slap T'Pol around for being a needless thorn in Trip's side. She's all over his case for being friendly with Liana, and reminds him of how he got pregnant in "Unexpected" — something which I'd like to point out to T'Pol was hardly Trip's fault (unless he missed the lesson at Starfleet Academy that said, "For human males to avoid getting pregnant by Xyrillian females, you must be sure not to put your hands in a box of granules while sitting in a holographic boat").
Probably the best thing about the mystery was revealing it at the end of the third act and thus leaving the fourth act in the hands of a good deal of heartfelt dialog and human choices. Ezral turns out to be a real person instead of just a vessel for the plot. He had to make a choice — saving his daughter's life in the heat of a crisis — that indirectly caused the deaths of most of his ship's crew, his wife included. Now he just wants what's best for his daughter, and for years that has meant raising her with this virtual family — but now we suspect she's ready to move on to real life while he's content to live in this virtual past. The always-reliable Rene Auberjonois brings a wonderful authenticity to Ezral's regrets, pains, and fears in a way that really makes a difference. Where this story could've fallen victim to its own familiarity, the actors make it watchable.
Beyond that I have little to say. "Oasis" is ultimately a simple tale of human choices and with a little bit of good character study. It's a credit to the actors — especially Auberjonois — that we're invited to care. It's somewhat unfortunate that such well-delivered tones of pleasantness and classic Trekkian attitudes must play themselves out in a plot that's so obviously routine. Three acts of pedestrian "mystery" and one act of sincere sentiment add up to an episode that I wasn't sorry to be watching, but also wouldn't be breaking down any doors to see again.