Back in the day, the day being post-WWII, pre-sexual revolution, Alfred C. Kinsey was America's boogeyman: He peeked under the nation's petticoats, eavesdropped in bedrooms, taking notes the whole time and exposing us for being -- gasp! -- libidinous beings whose carnal tastes weren't confined to mere procreation. He exposed us, and he did it in the name of Science.

Kinsey may have been a buttoned-up zoologist with a mountain of research to back up his findings, but he was also a freakazoid of major proportions: He encouraged, even demanded open marriage among his underlings, frequented bathhouses, had affairs with men, and filmed himself having sex with some of his subjects (his wife changed the sheets and served refreshments). He died in 1956, but Kinsey remains a controversial figure, a man over whose life biographers still bicker. Today, Kinsey is hot: T.C. Boyle's latest novel fictionalizes Kinsey's life. The Kinsey Institute for Research in Sex, Gender and Reproduction at Indiana University lives on. And now there's the movie "Kinsey," starring Liam Neeson, Laura Linney and Peter Sarsgaard and filled with celebrity cameos.

"Kinsey" is written and directed by Bill Condon, the talent behind the wonderful biopic "Gods & Monsters," but here there is little of the imaginative renderings of his previous effort. For all its explosive material, this is a fairly straightforward telling. Condon's instinct to underplay is on target; this isn't a story that needs a lot of embellishment. Still, there's a flatness to the filmmaking; what's needed here is a lot more va-va in its va-va-voom.

Told mostly in flashbacks interspersed with black-and-white "interviews" done in extreme close-up, this is a story without your classic narrative arc, i.e., hero encounters conflict, overcomes conflict, becomes changed by said conflict. So the hurdle Kinsey faces two-thirds of the way through the picture is too little, too late. Even once he discovers the joys of sex, he doesn't change much. Kinsey doesn't grow as a character so much as he mutates.

So without these classic elements to shape the story, it's up to Neeson to carry the film. And carry it he does. Indeed, it is Neeson's forceful performance -- not to mention the titillating subject matter -- that kidnaps the imagination, handcuffs it and drags it through the film's somewhat flat conclusion.

Heavy-browed and earnest, bow-tied and bumbling, Neeson's Kinsey is an awkward sort, a social maladroit more at home dissecting the mating habits of gall wasps than in pitching woo with female hominids. The movie, of course, provides a reason for this. He had your basic Hollywoodesque hellish childhood: Wimpy mom; punishing preacher dad who believed that everything modern man created, from electricity to telephones to zippers, was the handiwork of Satan.

Kinsey remains a virgin until well after his wedding night, when he and Mac (Linney), his first and only love, have considerable trouble doing the do. A quick -- and exceedingly funny -- trip to the family doctor reveals the source of the problem, and they're suddenly swinging in places they never knew they could swing from.

Theirs is a love story for grown-ups, sweet, tender, troubled and yet enduring. Linney, wrestling with a thinly written part, evokes a tsunami of emotion in a look and a gesture, bringing bright colors to a brown wren of a woman who discovers her own voracious sexuality while standing by her man, even as her man gets increasingly freaky in the sack.

About the sack part: This is, above all, a film about sex, and the depiction of sex is at times graphic. There's full-frontal male nudity; close-ups of aroused genitalia; threesomes filmed in black and white. But sex should not be confused with sexy. Forget about eroticism. Therein lies Kinsey's greatest shortcomings. He embraced sex with the fervor of a clinician, never quite coming to terms with the complexity of emotions and romantic entanglements.

Kinsey (118 minutes, at area theaters) is rated R for pervasive sexual content, including some graphic images and descriptions.

As wife Mac, Laura Linney discovers her own sexuality while standing by her man, Liam Neeson as Alfred Kinsey.