Grade: C

An all-too-strenuous shift of tone about two-thirds of the way through its modest running-time marks–and undermines–“The Fluffer,” Richard Glatzer and Wash West’s movie about Sean McGinnis (Michael Cunio), a naive young gay guy who gets involved in a porno video business in L.A. because of his fascination with the company’s leading man Johnny Rebel (Scott Gurney). Eventually, in addition to his cameraman duties, he’s called upon to help the object of his obsession prepare for his big scenes by providing some physical stimulation; hence the title. Johnny, however, is not only straight–indeed, he’s just gotten his dancer-girlfriend Julie (Roxanne Day) pregnant–but he’s obstinately oblivious to Sean’s interest. Unfortunately, Johnny is also an addict and an utterly irresponsible fellow. As it turns out, all his relationships–as well as his career–are doomed.

For most of its running-time, “The Fluffer” is a modestly amusing little comedy set in an interesting milieu and featuring some quirkily eccentric supporting characters. With Johnny’s descent, however, it abruptly turns into a dark melodrama, somewhat reminiscent of the odd-couple pairing of “Midnight Cowboy,” complete with death, flight from the law and betrayal. Unfortunately, the performers and filmmakers, who carried off the earlier portions of the picture reasonably well, prove not quite up to the seriousness of the last act. In particular Gurney, whose hunky cluelessness seems fine during the first few reels, seems to be straining uncomfortably by the close; and ending his appearance with a beachfront shot that mimics last image of “The 400 Blows” is a bad miscalculation.

Along the way, though, there are minor pleasures to be had in more offbeat, affectionate earlier parts of the picture, with veterans like Robert Walden (whom you might recall from the old “Lou Grant” series) and Richard Riehle (currently the crotchety grandpa on “Grounded for Life”) bringing some sparkle and bite to the proceedings and providing needed contrast to Cunio’s reticent, shambling Sean. (Sean’s tryst with a nice fellow named Brian, played by Josh Holland, could have added some heft to the character, but it’s a plot thread that’s quickly dropped.) Technically the picture is adequate, certainly far superior to the standard one finds in the kind of movies it’s describing.

“The Fluffer” can’t be described as much more than mildly intriguing, and its dramatic turn toward the close is a downer in more ways than one. But it’s certainly inoffensive, apart from a few brief nude shots that could trouble more puritanical viewers, and it treats the Hollywood underground with greater perception than one might have anticipated.