Bill Condon is an old hand on Hollywood’s eccentric-sex beat. He earned a screenplay Oscar for Gods and Monsters, the brilliant biopic about director James Whale, who gave Frankenstein a queer-eye-for-the-undead-guy movie makeover. Now he unveils his naked-truth portrait of the big sexual enchilada in Kinsey.

Alfred Kinsey (1894–1956) was the pioneering scientist whose epic study, Sexual Behavior in the Human Male, hit the nation like a sociological nuke in 1948. Who knew 95 percent of American men had violated at least one sex law on the books?

KINSEY ( * * * )
Directed by Bill Condon
Starring Liam Neeson, Laura Linney, Chris O’Donnell, Peter Sarsgaard, John Lithgow.
(Rated R, 118 min)

Nobody, until Kinsey’s candid interviews with 18,000 indiscreet citizens blew the whistle on the American bedroom. “The Kinsey Report,” as a gob-smacked public called it, whisked the mild-mannered Midwestern professor to the best-seller list and the cover of Time. But when he released the 1953 companion volume on female sexuality, he got in big trouble. Who wanted to know that 62 percent of nice girls masturbated, or that most brides had achieved orgasm long before the wedding night?

Writer-director Condon portrays Kinsey as a hanky-panky evangelist. Liam Neeson is ideal to play the bow-tied, buttoned-down man who unbuttoned a nation. Condon depicts Kinsey as the mirror image of his hellfire-preaching, Sunday schoolmaster daddy (John Lithgow) who warns that the zipper is the devil’s invention, giving “speedy access to moral oblivion.”

Laura Linney outperforms Neeson as Mrs. Kinsey, his former student and tireless academic ally. Years after his death, the Kinsey Institute abashedly confessed that, yes, his circle was a nonstop orgy among nerds. Kinsey sampled both sexes and sundry oddball acts.

Mrs. Kinsey, a loyal wife and remarkably homely (Linney fought the director to make her more so), hopped from bed to bed with mattress-back abandon. Peter Sarsgaard sizzles as a researcher who found it a pleasure to work under both Mr. and Mrs. Kinsey.

Sex aside, she was the most beloved figure on the scene. Her social graces mitigated his clueless tendency to alienate people by talking at them like mere specimens to be studied.

Rich costumes, jazzy set design, alert cinematography, smart dialogue, and evocative period tunes delightfully transport us back half a century, and the huge cast does its stuff with brio. This brings up one of the movie’s two big problems. There are more than a hundred speaking parts. The countless interviewees singing the body electric overpopulate the picture. And, many scenes are teases: When we walk into a gay bar frequented by Gore Vidal’s glittering cronies, we want to linger, but Condon whisks us in and out. Except for the climactic, virtuosically operatic monologue by Lynn Redgrave (Neeson’s aunt-in-law) as a lesbian saved from suicide by the Kinsey Report, and a particularly horrifying pedophile (William Sadler), few interviewees really get a chance to register.

Even Kinsey’s inner circle gets short shrift. Sarsgaard comes off as a bright boy toy with a nice tush but no motives. Chris O’Donnell and Tim Hutton sketch the perils of wife-swapping researchers so fast we barely know they’re there. Only the Kinseys are fleshed out, and less so than in a film without a cast of hundreds. Condon’s film throws lots of stylish light on sex. But he leaves too much of Kinsey’s soul in the closet.