Based on the premise that two headless torsos are better than one, the two-part CBS movie "Doubletake" -- which airs tomorrow and Tuesday from 9 to 11 p.m. -- achieves a new level of prime-time psychobabble not intended for the Maalox set.

Even the most jaded viewer will find this grisly tale, taken from the best-selling novel "Switch" by William Bayer, a little hard to stomach. One good thing might come of it, though. Congress might finally pass a law requiring that all blond women must, repeat, must install clear shower curtains in their bathrooms.

"Doubletake" borrows elements from a flotilla of familiar flicks -- including "Psycho," "Rear Window," "Dressed to Kill," "Body Double" and "Witness" -- and throws in a smattering of "Serpico" for good measure, mimicking the genre so self-consciously that it's hard not to smirk between the squeams. It's television imitating Brian de Palma imitating Hitchcock. But in between the predictable plot twists are some riveting moments, and Richard Crenna, looking craggier than ever, is not only likeable but believable in the starring role.

Part 1 opens with a double homicide. One victim is a repressed young schoolteacher, the other a beautiful prostitute. Both are blond. Both are decapitated, and the killer switches the victims' heads and arranges them in a gruesome tableau.

"Believe me, it's your kind of case," says the police captain to detective Frank Janek (Crenna). "In a city full of weirdos, we have got ourselves a number one whacko."

Either that, or Diane Arbus is back.

Surveying the crime scene, Janek quickly sizes up the situation: "The killer knew them both . . . Some kind of madonna-whore complex, putting a prostitute's head on a goody-goody schoolteacher like he was trying to rearrange their personalities."

Janek assembles a team of detectives led by veteran stage actor Cliff Gorman, whose Noo Yawk accent is so thick it sounds like he's got pushpins in his mouth. Meanwhile, at the funeral of an old friend and fellow cop, Janek meets Caroline Wallace (Beverly D'Angelo), a beautiful photographer with a mysterious past and a penchant for pectorals. "I'm doing a book on men who feel stress in their work, like boxers," she tells him. "I'm calling it 'Aggression.' "

D'Angelo seduces Janek after serving him a Chinese dinner ("I don't do carry-out"), and in between the Laura Ashley sheets, he enlists her aid in solving the murder.

Things are a little slow going at times, with plenty of dramatic padding to establish Crenna's credentials as the hard-boiled but sensitive cop. We know he's sensitive because he dries the dishes, plays the lute and says things like "Maybe I was a lousy husband."

He's also a man obsessed with delving into people's lives, fascinated, as he explains to Caroline, with "that thing that we're always looking for." You know, "the dark side."

Guaranteed to keep you guessing, plaid-jacketed cops pursue a parade of red herrings, including pimps, prostitutes, aerobics instructors and the requisite gay schoolteacher and hairdresser ("How many heads do you do a week?") while a subplot on police corruption starts to simmer.

In the end, Janek does unmask the killer, who definitely has two sides -- dark and darker. He also gets the girl and cleans up the department. What more could you ask from a four-hour movie?

As the killer says, "Whores. They're trash, but at least they admit it."

That goes double for "Doubletake."