In the two-hour premiere, a rogue experiment threatens not only the town, but perhaps the world, creating a portal that swallows everything in its path. So while discovering the ins and outs of the town, Jack also joins in solving the mystery of who's behind this new threat, culminating in the not-very-surprising decision (it's a series, after all) to have him stay on as town sheriff.

Ferguson (whose credits include NBC's short-lived comedy "Coupling") has a breezy comic presence, and he makes an appropriately wide-eyed guide through "Eureka's" many wonders, along with the teenage daughter (Jordan Hinson) who brought him through this neck of the woods in the first place.

The producers, in fact, have assembled a top-notch cast, which, in addition to Ferguson and Richardson-Whitfield, features Joe Morton as one of the resident geniuses, Debrah Farentino as an alluring psychologist and Matt Frewer as Aussie big-game hunter chasing a preternaturally evasive dog. (Greg Germann and Maury Chaykin are also featured in the launch but won't be around for the show.)

On the down side, series creator Andrew Cosby's intriguing framework evinces a somewhat uneven tone that makes abrupt leaps from quirky to dark. As a consequence, the premiere and a subsequent episode previewed are both diverting but beg the question of whether the show can consistently provide a fresh supply of menaces and mad scientists for Carter and company to thwart.

Sci Fi has at least reeled in a fish-out-of-water format that doesn't rely on Cylons or special effects, establishing a world of more down-to-earth wonders. The marketing challenge is whether the series will be distinctive enough for the cable net, as opposed to becoming "Everwood" with cool gadgetry.

In short, "Eureka" must still demonstrate there's more here than just its "A-ha!" premise. Then again, when it comes to episodic TV, necessity truly is the mother of invention.