Sex is easy in the world of John Cameron Mitchell's "Shortbus," where the deed is as explicit as many hardcore porn flicks. It's emotional connection - and the occasional orgasm - that are tough to come by.

Following Mitchell's delightful 2001 rock musical "Hedwig and the Angry Inch," the director's "Shortbus" is another marvellous mix of very adult, very overt themes and images coupled with a sense of childlike innocence and awe.

For all their fornicating, oral sex and other carnal acts, the characters feel like grown-ups reverting to experimental teen years, men and women given a chance to strip away adult hang-ups and put down a base for more honest, unrestrained love and sensuality in the future.

That's one of the key objectives for Mitchell and his daring cast of unknowns - to shake up notions of what constitutes a healthy relationship and sex life. Mitchell aims for shock value from the start, revelling in real on-screen sex acts not for their titillation value but as a beachhead to loosen up viewers and get them to re-evaluate their own relations.

"Shortbus" is not pornography, though some may simply call it porn with a better narrative disguise than most skin flicks. The characters are genuine and likable, and despite their lusty alternative lifestyles, their problems and perplexities are familiar.

The fact that they're actually getting it on, with real orgasms and ejaculations, is just another of Mitchell's dramatic tools.

The film's clever opening montage is an icebreaker for what's to come, the action zipping through a fantasyscape of Manhattan to introduce the characters at erotic play and brace audiences for the sexual intensity that permeates the story.

With the initial sex out of the way, we learn who these people are and how their lives intersect. Sofia (Sook-Yin Lee) is a sex therapist who has never had an orgasm, faking it for years with husband Rob (Raphael Barker).

Sofia's patients include James (Paul Dawson), who has an ulterior motive for suggesting to his lover Jamie (PJ DeBoy) that they expand their sexual relationship to include other men.

When they learn of Sofia's sexual secret, James and Jamie invite her to the Shortbus salon, the loft of Justin Bond (played by Manhattan performance artist Justin Bond), a place where bohemian New Yorkers gather for impassioned discussions of art, culture and politics, as well as anything from couple's sex to all-out orgies.

Sofia makes a connection with dominatrix Severin (Lindsay Beamish), who helps the sex therapist cope with her bedroom barriers in exchange for guidance in overcoming her own emotional isolation.

James and Jamie find a suitable third partner in Ceth (Jay Brannan), whose arrival prompts tough action from Caleb (Peter Stickles), a voyeur who has been benignly watching over James and Jamie from a distance.

A colourful ensemble of minor characters swirl about the lead players, highlighted by some gleeful moments with an elderly Shortbus regular (Alan Mandell) claiming to be a former New York City mayor.

The action turns darkly serious for some characters, though as with "Hedwig," a sense of whimsy prevails.

Mitchell and the cast developed the characters and story through long months of workshops and improvisations, the actors delivering spirited and sincere performances. For all that effort, some of the characters come off a tad superficial, like figures in a grand stage burlesque.

The sex is integrated so naturally that it simply becomes another part of the storytelling, never feeling lewd or gratuitous. The film works its way to a magical climax both sexually and dramatically in an animated sequence of the New York skyline that hearkens back to the beginning.

What the characters of "Shortbus" learn on their sexual journeys is by no means profound. But the ardour, boldness and merriment Mitchell applies in getting them to their destination makes it a worthwhile ride.

Three stars out of four.