"With the state of the world today, an alien intervention might be just what the doctor ordered." — Nigel Fenway (Brent Spiner) in "Threshold"

Some shows are well done. Some tap the public mood. CBS' "Threshold" locks us in the front seat of a superb thrill ride through modern terror and fantasy.

The series is rooted in a familiar sci-fi tradition. It hearkens to the "Star Trek" shows, films like "The Day the Earth Stood Still" and Wellesian novels that use extraterrestrial invasion to upset human smugness.

Given 9/11 and Hurricane Katrina, what could be more timely than a surprise that tests our national ability to keep it together?

"Threshold," which has a two-hour debut at 9 tonight, never feels less than sharp. It's built with great craftsmanship around imaginative plotting from executive producers Brannon Braga ("Enterprise"), David Heyman ("Harry Potter and the Prisoner of Azkaban") and David Goyer ("Batman Begins").

Carla Gugino, previously hard-drinking federal agent "Karen Sisco," brings her distinctive toughness and vulnerability to the starring role.

She plays Dr. Molly Anne Caffrey, a think-tank expert in charge of designing response plans to worst-case scenarios for the U.S. government. Caffrey's loner lifestyle is alleviated by the presence of an endearing pet bulldog named Monster.

As the pilot reveals, however, it's hard for Caffrey not to want what others may consider disaster — the violent arrival of aliens on Earth.

The opening minutes of "Threshold" lay out this scenario in gripping fashion. A ship at sea starts getting strange indications of an odd presence nearby; the holocaust that ensues in a dazzling display of special effects both horrifies and tantalizes us.

And that's exactly how we're supposed to react. For all the fear that "Threshold" deliberately awakens, it's balanced by the anticipatory thrill of guessing what the newcomers want — an argument echoed by the show's characters.

The government is skeptical. Its representatives are Deputy National Security Adviser J.T. Baylock (Charles Dutton) and hunky covert operative Cavennaugh (Brian Van Holt), who accompanies Caffrey and her team on their visit to what's now a ghost ship.

The team provides an interesting subplot. Their responses to evidence of an extraterrestrial infiltration offer an outlet for different views and comic relief.

It's a classic oddball group boosted by terrific actors: Nigel Fenway (Brent Spiner), a disaffected '60s radical and former NASA employee; Lucas Pegg (Rob Benedict), a youthful, Bible-toting astrophysicist; and Arthur Ramsey (Peter Dinklage), a womanizing cynic with very handy math and linguistic skills.

As they examine evidence aboard the ghoulish vessel, an already-jittery viewing experience gets jacked to new levels. Roaches scurry across the deck in a mysterious fractal pattern that becomes an ominous calling card. Caffrey and others watch video footage that soon will invade their brains in the most vivid, hallucinatory form.

Meanwhile, one survivor's DNA proves key to the aliens' method, if not motive: They're using auditory signals to unzip and alter humankind's genetic structure.

Hour two brings the action down to a more intimate scale, then climaxes with a vast cinematic shot that displays the full extent of the visitors' presence.

Such bold flourishes counteract a few minor quibbles with plot logic. By the time "Threshold" finishes tonight, there are more things in heaven and Earth than we ever may have wanted in our dreams.

Doubling down

Tonight at 8:30 marks the arrival of The WB's "Twins," a sitcom about two very different sisters who take over the family lingerie business.

"Twins" comes from "Will & Grace" creators David Kohan and Max Mutchnick and is on a par with recent seasons of the latter: shrill, vulgar and with little new to say about sexual identity.

However, "Twins" does have a cherry spot right after the established 8 p.m. hit "What I Like About You." That might be enough for undemanding young female fans.

Twin No. 1 is the smart and plain-faced Mitchee. She's played by Sara Gilbert, who displays great milking ability from thin material. Twin No. 2 is Farrah, portrayed by Molly Stanton. She displays an impeccable figure in the underwear that constitutes most of her wardrobe.

The purported intent of "Twins" is to send up these female stereotypes. But the pilot failed to reveal Farrah's secret 150 IQ or Mitchee's inner vamp.

Their ongoing quarrels are paralleled by battling parents. As Dad, Mark-Linn Baker doesn't contribute much beyond a vaguely conciliatory presence.

Melanie Griffith is more of a lost opportunity in the role of Mom. There's no one quite like Griffith on the planet, and with better lines, she can be hilarious, as she proved at a press conference last summer.

Although "Twins" apes The WB's cozy family image, a more Darwinian message seeps through. The world needs hotties to sell the stuff that geeks create. Divorce is bad for business. They all lived practically ever after.

Kay McFadden: kmcfadden@seattletimes.com