In brief: Early promise that quickly gives way to an overbaked stew of routine silliness.

Here's an episode that begins as epic, great-looking sci-fi, and continues through its first act as a story hinting at developing an interesting look at a truly different type of life form (for the crew, although not for Trek viewers) as well as looking back at human existence from their viewpoint. Promising material. But then it becomes a downhill slide, with a hostile invasion-of-the-body-snatchers plot that takes over, and eventually we end up just recycling lame-brained Trek cliches and assorted oddities.

"The Crossing" is another Enterprise failure, one that starts with the promise of awe but then quickly takes the path of routine rehashes. About the awe factor: Let's start with that first act. It's a winner. The Enterprise is swallowed up by a huge ship that promptly reconfigures its internal atmosphere to suit our crew's breathing needs (although why this is necessary is not clear, since our explorers never get out of their EVA suits once leaving the Enterprise). The ship's interior is a huge open room with cold, metallic surfaces and complex designs. Visually, this is great stuff -- the sort of grand sights we imagine when we think of visual science fiction. Kudos to the CGI designers and the FX wizards who make this an eye-pleasing and convincing scene.

While he's down here on the floor of the big room of this impressive vessel, an entity that resembles a cloud of gas and light permeates Trip's EVA suit and enters his head. It then leaves, apparently taking Trip's consciousness right out of his body and replacing it with a different, alien consciousness. After a moment, it returns Trip's mind to him. For Trip, the experience is beyond description; he literally left his body and existed without corporeal form.

That is an intriguing sci-fi concept that has possibilities. Indeed, the episode even hints at some philosophical discussion when the entity again enters Trip's body and then speaks through him, telling Archer in a curious and wondrous tone, "You're very interesting -- trapped in bodies that need maintenance." It takes pleasure in the simple experience of sampling a dozen items from the mess hall's menu. "You eat ... food," it exclaims.

But the thing about sci-fi concepts is that after you have a concept you need to do something with it. The approach of the makers of Enterprise, however, is to reduce a grand idea to the most mundane and cliche-ridden alien-takeover premise possible. The Trip-alien says to Archer: "You claim to be an explorer, captain. Open your mind to new possibilities." I was nodding in agreement at this point, wondering why Archer couldn't see the opportunity here to learn something new rather than constantly waiting for the other shoe to drop. But the thing is, of course there's another shoe to drop; Archer knows better than anyone that he is on a show called Enterprise, which is usually about fending off tangible threats instead of exploring new realms, whether physical or philosophical.

On TNG, this concept probably would have been used to develop some sort of understanding about human nature or other realms of existence (I'm reminded of the leap of imagination in a seemingly but not actually threatening episode like "The Nth Degree"). But on Enterprise it's a plot device to bring about obvious action that we've seen time and time again. What we have here is the most potentially interesting sci-fi concept this season employed merely to propel a ship-takeover plot. Why bother?

Once this plot is set into motion, the crew is quick to discover that these alien entities want control of their bodies for selfish reasons. There's a sequence where an alien takes control of Lt. Reed and then embarks on a corporeal mission whose main priority is apparently getting laid. He engages in odd conversation with a female crewman on the turbolift ("You are female," he observes helpfully). When that encounter doesn't pan out he shows up at T'Pol's quarters, leading to a shameless and completely goofy scene that lies somewhere between laughable and tacky, pandering to those in the audience who want nothing more than to see Jolene Blalock's Hot Bod [TM]. We've got T'Pol in tight underwear as the camera pushes her breasts through the plane of our television screens. The Reed-alien makes campy sexual overtures by way of the kind of bad dialog that makes you laugh in disbelief. Talk about limited imagination: Non-corporeal beings take human form not to gain insight or understanding, but to get into someone's pants.

Meanwhile, more crew members have their bodies snatched and Archer faces a complete takeover of his ship. He starts locking affected crew members in their quarters. Then Mayweather discovers that the alien entities can't pass through the shielding in the catwalk, so Archer has the entire crew reassigned to the catwalk, a plot idea that feels awfully redundant considering that in December we had a whole show called "The Catwalk" where the crew took refuge up there.

There's also use of T'Pol's special Vulcan mental disciplines, which makes it possible for her to be inhabited by one of the alien entities without being controlled by it. This permits her to learn the aliens' true motives for taking over the ship, which is that their own ship is ceasing to function, which means they will die if they don't take control of a new ship.

The crew's solution to the predicament is another one of those protracted mechanical tasks where nothing dramatic is happening on the screen and it feels more like a way to fill time. Phlox figures out a way to knock out all the infected crew members and drive out the alien entities. This involves him exposing the crew to a mixture of gas that he rigs up by rearranging things behind a panel in an obscure corner of the ship, while Archer has to talk him through which levers to pull and which valves to open. This is narrative quicksand. It's arbitrary prop manipulation captured on film -- the "Minefield" bomb-dissection approach to filmmaking without the benefit of that show's character development. And the walk-through dialog is bafflingly extraneous. After Archer tells Phlox to remove a panel, Phlox then asks him what to do with it. Archer says to do whatever he wants with it -- like set it on the floor. And I'm asking myself, is this exchange even necessary in the slightest?

I also was confused as to where the affected crew members' conscious minds went when the aliens were in their bodies. It's established that they are removed. Were they just floating around the ship? And when the entities were driven out, just what would motivate them to return the crew's minds to them? Such details are not really worth questioning, I suppose, but the plot is on arbitrary, shaky ground and thus comes off as unconvincing.

There are a couple scenes that work. As I've said, the early parts with Trip are worthwhile. And later on, I thought the Hoshi-alien's disturbingly calm call for help for her "broken leg" was eerily depicted; a close-up on Hoshi effectively conveys some subdued, suspicious menace. But more often the show is lost in muted half-hearted performances, like T'Pol's "trust me" appeal to Archer on risking herself to confront the entities -- a scene that, as acted, completely lacks conviction.

I also was less than thrilled by the ending that blows up the alien ship and all the non-corporeal life forms. Given the level of the threat, I don't blame Archer for this course of action. But there's something depressing about the whole idea that the episode begins with such higher-minded would-be intentions, only to turn it into a lowbrow alien conspiracy and end with them being categorically destroyed. It's a cynical and unmoving arc.

I'm thinking that Enterprise needs to show us something new, reinvigorate itself with some energy and purpose, or return to its characters. This stretch of the season has been a string of unrelenting mediocrity that the creators would be well-advised to break themselves free of at once. Of course, I'm sure they're telling themselves that. Or at least I hope so. I hope they don't actually think "The Crossing" is exciting television.

Next week: Enterprise borrows the courtroom scene from Star Trek VI to give Archer a taste of justice, Klingon style.

Previous episode: Canamar
Next episode: Judgment