Watching the Detectives would like to be a screwball romantic comedy in the tradition of What's Up, Doc? , but it confuses kookiness with mental illness. As romantic comedies go, its heart is definitely in the right place, but its head is in a much more precarious position.

Neil (Cillian Murphy) is an amiable guy down on his luck. A certified movie geek, he owns a modest video store (it sells VHS tapes, if that tells you anything) being crowded out by a Blockbuster-type franchise named, appropriately enough, Media Giant. His unsupportive girlfriend (Heather Burns) kicks him to the curb after he subjects her to an oddly passive-aggressive prank; Neil has a waiter spill a glass of water in her lap so he can gauge her reaction. We don't have much time to assess what a creepy move that is on Neil's part, since into his store blows the attractive, wacky and altogether unpredictable Violet (Lucy Liu).

He's a cinephile; she creates her own adventures. He's uptight; she's spontaneous; blah, blah, blah. You get the idea. After the obligatory meet-cute, Neil and Violet go on an eventful first date. Violet, we soon learn, is an Olympic champion when it comes to head games. She pretends to be hammered, ostensibly to test Neil's chivalry. Later that evening, Violet coerces Neil into burglarizing a Media Giant outlet for the mischief of putting videotapes in the wrong cases.

That larceny leads to still more opportunities for Violet to prey upon Neil's gullibility and anxiety. She fools him into thinking the cops are hot on his trail for the break-in. Just for good measure, she enlists a friend to portray a police detective eager to sodomize Neil. Laughing yet? Why wouldn't Neil run as far as he could in the other direction? If the film's musical cues weren't so incongruously sunny, you might think Watching the Detectives owes more to Play Misty for Me than Bringing Up Baby.

Writer-director Paul Soter, part of the comedy troupe Broken Lizard, explores some promising ideas and has a game cast, but his direction is lead-footed. We supposedly know Neil is a film fanatic because he owns a video store and makes at least one passing reference to Butch Cassidy and the Sundance Kid, but there isn't much else to illuminate his character. Memo to Mr. Soter: Show, don't tell.

More crippling is this: Watching the Detectives just isn't very funny. The jokes are variations on more successful gags from other, better movies. When Neil's ex-girlfriend tells him she was "faking it" when she claimed to appreciate Ingmar Bergman's Seventh Seal, she launches into a fake orgasm of pedanticism. Cute idea, sure, but the gag is embarrassingly lame.

The cast is a mixed bag. Liu is as appealing as she can be playing an obnoxious lunatic. Murphy isn't offensively bad, by any means, but he makes an ineffectual romantic lead; anyone who has seen the actor's onscreen villainous side (Batman Begins, Red Eye, etc.) knows his talents are utterly wasted here. Michael Panes and Saturday Night Live's Jason Sudeikis have the roles of Neil's smartass buddies, but nothing they say is particularly smart, and much of it is only half-assed.

The anamorphic widescreen picture is strong and clear, possessing clean lines and generally detailed. Aspect ratio is 1.85:1.

Watching the Detectives is primarily dialogue-driven, but its Dolby Digital 5.1 actually makes effective use of rear speakers for a full sound experience. No foreign-language tracks or subtitles are available.

A trailer is the sole bonus.

I wish I could have liked Watching the Detectives more. It's well-intentioned. It isn't mean-spirited. It doesn't load up on foul-mouthed insults, pop culture references or scatological humor. Alas, Watching the Detectives is a rom-com that lacks romance and comedy.