Who knows? Maybe he developed writer's block. Or joined Up With People. Or dropped dead from shock the day Bush got re-elected. In any event, the notorious Northern California serial killer who called himself, rather grandiosely, the Zodiac, hasn't fired off a single letter to the editor since April 1978. That used to be his MO, as anyone who has studied his reign of terror in the '60s and '70s can tell you kill or maim someone, then send a terse little note of self-congratulation to The San Francisco Chronicle or the Vallejo Tribune, quite often decorated with a bit of double-talk or a baffling cryptogram. This was a psychopath with an obvious need for attention perhaps even a death wish. Why else would he sometimes dare to call the cops and taunt them?

Talk about an enduring cold case. In the decades since the Zodiac last struck (he claimed 37 victims; the authorities confirm just five, not including a few survivors of his attacks), Americans with a taste for the macabre have fixated on serial killers like John Wayne Gacy, Ted Bundy, Eileen Wuornos, the BTK Killer and the fictional monsters of The Silence of the Lambs, among others. But they've never quite given up their jones for the Zodiac because his case was never solved, his identity never revealed. In the aftermath, we've been inundated with a pile of related books, TV shows and movies. Today, there's an active Web site for amateur cybersleuths (www.zodiackiller.com), and half a dozen "researchers" continue to cook up more elaborate theories than the assorted crazies still crawling around Dealey Plaza and the wastes of Roswell, New Mexico.

Now comes The Zodiac, a low-budget indie rehash that contributes little to what, if you're generous, might be called the "literature" of the case. It's not as gory or cynical as some of its cinematic predecessors the one that immediately comes to mind is a 1971 atrocity called The Zodiac Killer, in which the slavering killer brained his victims with a rusty tire iron and worshiped at a homemade altar. But the new movie is not very compelling or convincing. Rookie director Alexander Bulkley, who wrote the screenplay with his brother Kelly, depends on the old obsessed-cop formula to propel the drama, and by the time beleaguered small-town detective Matt Parish (Justin Chambers, late of Liberty Heights) comes to the end of his rope, screaming at his wife (Robin Tunney) and swilling bourbon like a Sigma Chi at Mardi Gras, he's become so hysterically unlikable that you half hope the Z-Man will fall by the house and put the poor guy out of his miz.

As it happens, the Bulkley brothers are in no mood for mercy. They not only torment their fictional Vallejo cop for 98 minutes with the usual array of false leads and frustrating near-misses, but they torment us with a snail's-pace melodrama that never produces any real emotional tension or the climate of fear the moviemakers are shooting for. When their killer sneaks up on a pair of teenagers in a remote lovers' lane and shoots them to death, it's an oddly unaffecting moment, despite the crescent moon overhead and the cold-blooded mayhem on the ground. When we get fleeting, non-disclosure glimpses of the Zodiac (body by Marty Lindsey, voice by Brian Bloom), they don't draw us in either, because the film doesn't give the guy any texture. This could be anyone listening to the Giants game or playing Gilbert & Sullivan on his stereo set with a big American flag hanging on the wall. How the Bulkleys chose these particular details is anyone's guess (maybe they're buried somewhere in the "literature" too), but their failure to get under the Zodiac's skin is a major fault.

Meanwhile, everything gets under Detective Parish's skin his demanding boss (Philip Baker Hall), his wife, his fellow officers, even his cute little son, Johnny (Rory Culkin), who seems to have unlimited access to the local police station and who, against the odds and in defiance of the facts, comes up with a workable astrological angle that aids in the case. Simply said, the little shaver seems to have more insight into the criminal mind than all the cops, shrinks and nagging reporters put together. Talk about poetic license.

Anyone who knows the first thing about the actual case knows how the movie must end: in total frustration for the investigators. "The guy is a fucking ghost!" our Matt shouts. No kidding. So elusive is he, in fact, that The Zodiac has no theory of its own about who or what he was. Over the years, more than 2,500 people were considered Zodiac suspects, but none panned out. The most likely of them, Arthur Leigh Allen, died in 1991, his denials having been supported by DNA mismatches. In 2004, the San Francisco Police Department officially closed the case, but it will probably haunt serial killer buffs forever.

While this determined army sets out to solve the thing, we are left to consider the killer's final request, contained in the last of the 21 letters he sent to newspapers in his bloody heyday: "I am waiting for a good movie about me," the Zodiac wrote. Well, so are we, pal. So are we.