In the entertainment industry, when the second album or film project fails, it's said that the artist responsible has fallen prey to the dreaded "sophomore slump."

And there are several examples of more-talented (and less-talented) directors who have made worse second films than Kasi Lemmons. Still, you can't help feeling at least a little let down by "The Caveman's Valentine."

That's because Lemmons made her debut with the 1997 drama "Eve's Bayou," which became one of that year's biggest independent film success stories (it even wound up on several Top 10 lists).

What she's opted to make this time around is a real muddle. It's a less-than-compelling drama and a much-less-than-compelling murder mystery, and it squanders a first-rate cast.

That includes the always riveting Samuel L. Jackson, who stars as the "caveman" of the title, Romulus Ledbetter, a once-promising classical musician and devoted family man struggling with mental illness.

A paranoid schizophrenic, Romulus now finds himself homeless, living in a cave in a Manhattan park and suffering from nightmarish visions and delusions about a fictional adversary. However, he is content to live this tortured, solitary existence — at least until the outside world intrudes.

The cause for that is the discovery of the frozen body of a transient, found in a tree outside his cave. Luckily, the police officers investigating don't believe that Romulus is responsible, but they don't exactly believe his claims that the murder was committed by world-famous photographer David Leppenraub (Colm Feore).

So Romulus "cleans up," so to speak, to do some investigating of his own. In the meantime, he's also determined to reconcile his differences with his estranged daughter Lulu (Aunjanue Ellis), a police officer.

Despite Jackson's surprisingly subtle (and therefore watchable) performance, the film's treatment of mental illness isn't nearly as sensitive or well thought-out as it should be. And Lemmons never quite reconciles the disparate story elements. Consequently, the stark "reality" seems less realistic than the fleeting fantasy sequences, and the thriller itself never amounts to anything.

If there's anyone who should take issue with the film, it's author George Dawes Green, who has had yet another well-regarded novel massacred on the big screen (the first was 1996's ludicrous film version of "The Juror"). But since he wrote this clunky screen adaptation himself, much of the blame rests with him.

"The Caveman's Valentine" is rated R for frequent strong profanity, violence (beatings, a choking and gunfire), gore, full male and partial female nudity, simulated sex, a scene of torture and use of crude sexual slang terms. Running time: 105 minutes.

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