'Life as We Know It' employs a depressing plot twist

"Life As We Know It" thinks it's found the missing ingredient in the modern, moribund romantic comedy: gruesomeness.

Katherine Heigl and Josh Duhamel star as mismatched singles who are designated godparents to a cute baby, and they inherit the child when the mom and dad are KILLED IN A CAR CRASH.

This is all in the previews - no spoiler harm, no spoiler foul.

So the birth parents are dead, but not in a thoughtful way, wherein tragedy is part of the ongoing story, and some tinge of melancholy hangs on the edge of each successive scene.

No, they're dead in a screenplay convenience kind of way. Kooky characters make jokes at the funeral, and Heigl and Duhamel go from abject grief to changing poopy diapers in five seconds.

That's not the residue of sadness on Heigl's face, it's doody.

There is often, you may have noticed, a ruthless streak in romantic comedy. Individuals fated to fall in love are often paired with expendable significant others, who are summarily jettisoned so the predestined romance can commence.

But "Life as We Know It" takes this process to a new and nihilistic level - the expendable characters are not ditched, like Greg Kinnear and Parker Posey in "You've Got Mail." They're closed-casket dead.

This spasm of tastelessness stems from desperation. The traffic fatality is the one premise Hollywood hasn't tried with Heigl, who's been through the rom-com wringer - bridesmaid, taming of the shrew, I married a spy, I had to sleep with Seth Rogen.

One shivers to think where it might go from here. I'm picturing her in something postapocalyptic, like "The Road," meeting cute with Viggo Mortensen and his son. They dodge raindrops and cannibals in a montage backed by a He And She cover of Burt Bacharach.

It could hardly be worse than "Life as We know It," which puts Duhamel and Heigl in the dead couple's house - for the sake of the child, we're told, but really for the sake of the script.

Not long into the movie, Duhamel says, "this place is like a mausoleum," and starts taking down all pictures of the deceased. I'm not kidding.

This is one rewrite away from a horror movie, in which doppelgänger godparents actually kill the biological mother and father, and assume their lives.

And, yet, if you take away the creepy premise ("The Car Crash of Eddie's Father"), it's not the worst romantic comedy I've seen. That would probably be "Love Happens," about a grief counselor who falls for Jennifer Aniston, then helps a grieving contractor confront his son's job-site death by taking him to Home Depot.

Heigl and Duhamel are, in spite of almost everything, kind of cute. I take back the mean things I've said about Duhamel, which were born of "Transformers." In the role of unreconstructed bachelor, he's not bad. He's laid back without being dull, he makes Heigl a little less shrill (always the man's job on a Heigl movie), and he's prettier than Rogen.

Still, if romantic comedy is going to work again, Hollywood is going to have to deploy this chemistry in the service of a story that's not so grim, or derivative (can a women in a movie or credit card commercial own something besides a bakery?).

If Stephen King wrote a romantic comedy, this would be it.

Produced by Barry Josephson, Paul Brooks, directed by Greg Berlanti, written by Ian Deitchman, Kristen Rusk Robinson, music by Blake Neely, distributed by Warner Bros.