In brief: A solid nuts-and-bolts story, although I called the ending in advance.

Sometimes I wonder if the people who inhabit sci-fi stories have more willingness to suspend their disbelief than those of us in the real world. I guess they would have to. After all, if you live in a world where weird things can and do routinely happen, and the seemingly impossible is possible, an elaborate ruse like the one in "Stratagem" might feel all wrong, but your knowledge of how the world works would make the scenario seem logically plausible.

The plot of "Stratagem" plays like an episode of Mission: Impossible, and, indeed, a reader informs me that the show is a take on an old M:I episode called "Submarine," in which a similar plan was hatched. (They were always trying to trick the bad guys with elaborate stings in those M:I stories.) "Stratagem" is effective because it finds the right details, uses quick thinking and suspense instead of mindless action, and most importantly, puts us in the position of sympathizing with the villain even as we hope the ruse will foil him.

In my review of "Proving Ground" I made a point of the fact that the Xindi named Degra had been such an undefined presence that he might as well have been interchangeable. That's no longer the case after "Stratagem." Degra (Randy Oglesby) emerges as, if not quite a fully developed character, at least a full-fledged personality steeped in believable psychology.

Degra wakes up to find himself in a shuttle with Jonathan Archer, apparently three years after the last thing he remembers. A long-haired Archer tells him that the Xindi mission to destroy Earth was successful, but that the Xindi insectoids had merely used the Earth threat as a diversion to seize control of Xindi society. Degra had been imprisoned with Archer in the aftermath of both societies' downfalls. Degra can't remember anything because of temporary side effects from a truth agent administered in prison just before their escape.

Thank heavens this premise isn't explained with more time travel.

The twist -- and I liked how it was revealed to us -- is that the premise set three years in the future is actually an elaborate deception concocted by the crew of the Enterprise. The shuttle is actually a simulator room and Archer is feeding Degra bogus facts in the hopes he can elicit relevant information that will help the Enterprise find the location where the Xindi are building The Weapon.

This results in a game of skillful caution for both Archer and Degra. Degra doesn't fully believe what he is being told, but isn't quite sure what to think. Archer gets information relayed to him from the command center where T'Pol and Hoshi help run the simulation and consult Degra's personal logs. When they can't find the answers Archer needs to respond to Degra, Archer has to improvise. (I wonder: After capturing Degra and his team, could the crew really have conceived and implemented this elaborate plan in only three days?)

We also get our first indication since Gralik in "The Shipment" that the Xindi have some actual depth. Degra is shown as a man building a terrible weapon only because he has to protect his people -- and by personal extension, his children. He has a family he wants to be with, he has made personal sacrifices to serve his people, and he expresses regrets about the 7 million killed on Earth in the initial weapons test.

Oglesby turns in a solid performance that showcases a respectable acting range; we are forced to realize that he has been wasted on perfunctory (and repetitive) exposition scenes in a half-dozen other episodes this season.

The sticking point that remains, of course, is the whole muddled issue of the Xindi's underlying need to commit genocide based on information they've been supplied by an as-yet-unknown-to-us third party. As much as Degra here comes across as a reasonable man doing what he must for his society's survival, I'm still deeply troubled by the fact that there's no explaining the logic in the Xindi's answer that nothing short of the complete destruction of an entire world can counter an alleged threat.

It's also somewhat unfortunate that the Xindi story arc has, it seems, been reduced to a desperate hunt for the weapon set against a countdown to its launch. There's no longer time or reason for diplomacy or other information gathering, because the writers have set a deadline of only a few weeks and established fairly rigid boundaries.

What works here is the way the story's details are an exercise in precision: One wrong statement by Archer, or one technical glitch in the simulator at the wrong time, and the whole operation will be blown. Indeed, the scene where Degra finally begins to suspect he is being lied to -- while hiding a weapon behind his back -- is one of the better recent examples of suspense on this series. I will trade any 10 scenes of the MACOs shooting at people for one well-executed scene like this that stimulates the mind as well as the viscera.

Ultimately, the ruse is blown, but not before Degra has unwittingly given Archer the coordinates of a red giant where a Xindi military colony called Azati Prime is located. Could this be the base where the final weapon is being built? Degra later claims not, and with a ticking clock, Archer must decide what to do next. It's a three-week detour to the red giant -- a detour they can't afford to make if it's not the right location. (Although I now find myself asking, a "detour" from what alternative course of action? Perhaps I missed something.)

I admit I'm forced to wonder why Archer did not consider interrogation-by-airlock, but perhaps that's a can of worms best left where it lies.

To shorten the voyage, Archer orders Trip to investigate and adapt the Xindi starship's subspace vortex technology that allows them to jump quickly across light-years of space. Trip does so and launches the Enterprise into a vortex that threatens to rip the ship apart. Archer desperately grabs Degra and the Xindi engineer from the holding cell and demands they help stabilize the technology.

It's at this point where the twist upon the twist became fairly obvious to me -- that the whole use of the Xindi vortex technology was another simulated ruse to make it look like the Enterprise had so quickly traveled to Azati Prime. I just wonder if Degra would've really been taken in by this particular trick and let slip his outburst, considering he had just been through one elaborate deception already. What's the proverb Scotty once used? "Fool me once, shame on you. Fool me twice, shame on me."

No matter. My objections to such plot points aren't huge. "Stratagem" is a solid installment in the Xindi arc, in large part because of its straightforwardness and willingness to stick to characters and truthful behavior. The Enterprise crew gets a crucial piece of information, and the Enterprise writers pull it off skillfully.

Next week: Reed and Hayes go one-on-one, as do Trip and T'Pol.

Previous episode: Proving Ground
Next episode: Harbinger