In brief: Effective as atmosphere. Just don't look for much else.

"Impulse" is a workable outing of style trumping substance, and of aggressive production design trumping sometimes-goofy action. Action shows like "The Xindi" or last week's "Rajiin" don't do a whole lot for me because they're mostly transparent exercises with no edge. "Impulse," it must be said, is also a transparent exercise, but at least it has an edge, with enough grit to be entertainingly disorienting. The story may be slight at best, but these sort of shows, if pulled off, don't necessarily require much story. Atmosphere -- not insight -- is the name of the game. If you're looking for more, you're going to be disappointed. You have been warned.

In the couple hours before and during the time that I watched the tape of "Impulse," I drank a bottle of wine. I'm not sure whether that was a good idea or a bad one, but it did make the experience somewhat more ... sensory-driven. Not that I'm recommending alcohol consumption (or abuse) in the face of "Impulse," because as it is this is an episode that doesn't need any sensory enhancements. Watch it with the lights turned off. That ought to do the trick. An e-mail correspondent wrote to me, "I think I am on the verge of a seizure," after watching this episode. In that case, turn the lights back on (or drink a bottle of wine).

The Enterprise receives a distress signal from the Vulcan ship Seleya (as in Mount Seleya?), which was pulled into the expanse some time ago. The last Vulcan ship to enter the expanse -- the one that we learned in "The Expanse" was destroyed after its crew went mad -- was the Vankaara, which was actually sent in to find the missing Seleya. The Enterprise discovers the Seleya adrift in an asteroid field that also happens to be rich with Trellium ore. The away team (Archer, T'Pol, Reed, and MACO Hawkins) boards the Seleya to rescue its crew, but instead they find a battered ship and a crew of Vulcans who have been infected in some manner that turns them into violent monsters. In a paranoid, zombie-like state, they attack the away team. It is not open to discussion.

This is, I must admit, a plot somwhat reminiscent of the Andromeda episode "Dance of the Mayflies," a horrendous hour of action camp that in retrospect was a clear warning sign that I would not be an Andromeda viewer for much longer. The difference between "Mayflies" and "Impulse" is that "Mayflies" offered unwatchable camp while "Impulse" steers in the direction of respectably intense atmosphere. The show is just this side of plausible: The Vulcans may be implacable monsters who do not have the power of reason (so why have they not slaughtered each other, and why do they gang up on the away team, etc.?), but at least they aren't cartoon players. The action uses them within a semi-plausible physical world, in a horror-movie setting with unfriendly mise-en-scene rather than colorful bubble-gum flavors.

The Vulcans seal off the corridors so the away team cannot get back to their shuttle, so they must now fight their way through another route. At stake here is T'Pol, who is afflicted by the same condition that has doomed the Seleya crew to terminal insanity. T'Pol begins her own slow descent into madness and paranoia, becoming more of a liability for the away team than an ally. There are some scenes that work reasonably as tension, like when T'Pol pulls a phaser on Archer, who must then try to appeal to T'Pol's rapidly fading sense of logic. Jolene Blalock is game for these scenes, although her loss of control feels a little too "acted" to be genuinely effective.

Thinking too hard about any of this will only reveal the silliness of the plot. My advice: Don't. Okay, I will point out that it strikes me as unlikely that Vulcans whose emotions are allowed to run rampant would simply become perfect movie monsters interested only in killing everyone. I also find it a bit convenient that the Enterprise happens upon the Seleya at just the right time to find that the crew has gone insane but hasn't died of the illness or by their own hands.

It turns out that poisoning from the Trellium in the asteroid field is the cause of the Vulcans' condition, because it breaks down the neural pathways that allow them to suppress their emotions (or something). This has an interesting implication, because the Trellium that Trip and Mayweather salvage from the asteroid field can't be used to protect the ship from anomalies because it would kill T'Pol. The episode's one iota of substance comes when T'Pol volunteers to leave the ship so Archer can install the Trellium, and Archer refuses because T'Pol is part of his crew. Moving, no. Palatable, yes.

I also liked the pseudo-twist ending, where movie night segues into T'Pol's distressing nightmare. Psychological terror can make for some interesting imagery.

About all I can say is that either you like the execution of all this or you don't. David Livingston has opted to shoot most of the scenes aboard the Seleya with a shortened film exposure that gives the motion a harsher look -- a trendy technique that Enterprise has been using much more of lately, but one that fits the material here. There are also lots of nifty special-effects shots depicting a convincing asteroid field where big rocks are constantly slamming into and pulverizing one other. And inside the confines of the Seleya are strobe lights. Lots of strobe lights. Visually, this works; the cumulative effect manages to boost the show's intensity.

"Impulse" is sort of a guilty pleasure. It is entertaining solely for its superficial visual qualities -- hard metallic surfaces, gritty debris, stylized lighting, a cramped setting that manages to close in on the characters, horror-movie-inspired images that are about style rather than content. I can't commend this show on the basis of its substance, because there isn't any. But this is an episode that looks really good and works on its basic chosen level, which this week seems like enough for a qualified endorsement.

Next week: Hoshi. An alien. A big choice. (Hey, the preview didn't give me much to work with.)

Previous episode: Rajiin
Next episode: Exile