One way to understand the strange conflict at the heart of "Muckle Man, " the spooky world premiere by Roberto Aguirre-Sacasa now at City Theatre, is as a caution against the hubris of obsessive science.

Annie O'Neill/Post-Gazette Nathan Blew plays the "Muckle Man" and Robin Walsh is Marina in Roberto Aguirre-Sacasa's new play at City Theatre. Click photo for larger image. "The Muckle Man" Where: City Theatre, 57 S. 13th St., South Side. When: Through Feb. 18. Tues. 7 p.m.; Wed-Fri. 8 p.m.; Sat. 5:30 and 9 p.m.; Sun. 2 p.m.; some exceptions. Tickets: $15 to $45. 412-431-2489 or www.citytheatercompany.org. Note: Contains brief full male nudity. Related articles Stage Preview: Playwright with a new work at City Theatre went from 'Spider-man' to 'Muckle Man' 'Muckle Man' started as a Webbed creature (1/25/07)

But that would be imputing too serious and reactionary an intent to what is mainly a smart, crisply written and engrossing sci-fi narrative in which a mysterious creature does what aliens or the unknown usually do, intensify and illuminate human needs and passions.

The crispness is not only in much of the dialogue but in the broad strokes and quick jump cuts among more than two dozen scenes that tell the story.

Story is what "Muckle Man" is all about. Marine biologist Addison has brought his two sons and wife Marina (telling name) to a laboratory on Conception Bay (also suggestive) on the edge of Newfoundland (that, too!), which is as far out into the Atlantic as this continent extends, in pursuit of one of the mysteries of the frigid deep -- the architeuthis, the giant squid. But in his obsession, he neglects his family. When one son is drowned, a mysterious stranger appears -- just as Addison captures an architeuthis for study.

Other marine oddities begin to happen, and everything and everyone, including the squid, begins to change. Cue the spooky, oo-ee-oo-ee music.

But although "Muckle Man" teases us with inklings of monsters and such, it doesn't take that route. Instead, it sketches Marina's despair over the loss of one son and its effect on the other, and her subsequent interaction with the stranger from the sea. That parallels Addison's growing fixation, building toward, well, what?

The name that Addison gives the squid (for exploitation by National Geographic and the Discovery Channel, let alone People Magazine) is Sigmund. It's a silly name, but such humor is a big part of the play's appeal, found mainly in Marina's man-hungry sister, Dora (the explorer?), and Addison's cute, gay assistant, Gilbert, nicknamed Gil (gill?).

Aguirre-Sacasa writes so winningly for those two that I fear he'll be snapped up for sitcom writing, rather than go on building what promises to be a fine career as a playwright.

Does any Pittsburgh actress shine with such emotional transparency and a touch of the other-worldly as Robin Walsh? She glows with fearful wisdom and the intense recognition of the sacrifice Marina envisions.

The spot-on casting continues throughout, thanks to the canny eye of director Tracy Brigden. Tami Dixon is a riot as the randy, not-so-swift Dora, and as the surviving son, eighth-grader Joe Bender is quietly, even scarily, natural.

The three men are all welcome imports. James Lloyd Reynolds has the toughest job as Addison, for whom Aguirre-Sacasa doesn't write with the verve evident elsewhere, but Reynolds stays true to his character's generally unsympathetic nature. Nathan Blew is strong as the strange stranger, and Brett Mack is justifiably an audience favorite as wry Gilbert.

City's resident design wizards Tony Ferrieri (set) and Andrew David Ostrowski (lights) provide a house, beach and lab, backed by a sky across which forbidding clouds scud, lit by a misty moon. Light also dances along the edges of low glass walls, suggesting dunes and separation -- and cages. One imagined design feature is the glass tank in which the imagined architeuthis is held.

The play's title is made up, but it makes sense, fitting the abundant folklore of magical marine beasts. Architeuthis, though, is real. We're told (and shown, in a brief slide show), it has the largest eyes of any being on Earth. Even unseen, it is a powerful presence.

The play is short, perhaps 100 minutes, intermission included. I wanted more -- not a different ending, but some fuller connection between the stories of the beast and the humans. I can't quite fill out the parallels, but I'm working on it. Maybe the playwright is, too.