It’s hard being a serial killer.

Well, not the killing part. I mean — grab a knife, track a family and have yourself a bloody old time.

Rather, it’s hard to be a respectable serial killer. You think you have your victims planned out, a place to bury them and a way to make use of their skin, and what happens? Some nutjob in Wisconsin starts driving into town in a golf cart made of intestines.

But even if the knife set you spent your life savings on goes to waste, up until now, you’ve always been able to look to the morbid, repulsive imagination of the cinema for tips. After all, they know how to craft a good psychopath, right?

Not this year. Give your thanks to “The Stepfather,” a remake of the 1987 film of the same name. What could have been a well-twisted study of insanity born out of broken homes becomes nothing more than a commercial for bathing suits and Home Depot (Come in right now and get $10 off all human storage cabinet supplies!).

First off, we’re introduced to our stepfather (Dylan Walsh, “Nip/Tuck”), who has just woken up on Christmas morning. He puts on “Silent Night,” makes some peanut butter toast and packs his things as he casually steps over the bodies of his now discarded family.

Our stepfather, now known in Portland as David Harris, is shopping for his daily groceries when he meets Susan Harding (Sela Ward, “The Day After Tomorrow”)

and her lovely family. How does this seemingly sterling psychopath charm the pants off of the well-dressed divorc?e? He casually explains how the ring on his finger is just a formality — his wife died in a car crash. Harding gives a half-sympathetic frown, they have a chat and six months later they’re getting married.

But then the eldest Harding, Michael (Penn Badgley, “Gossip Girl”), had to get all hunky on us. Well, him and his girlfriend. He’s just come home from military school and isn’t very fond of his mother’s suitor. In fact, he’s not too fond of anything. But after a few shots of tequila and awkward repetitions of “Family is important,” he seems to gain their trust.

Yes, and this is all in the first 15 minutes. So, we’ve been given the very model of a modern major murderer. Perfect husband makes for a subtle killer, right?

Not if he’s a clumsy oaf.

He offs all the people who might have their suspicions about him in ways that would impress any forensic pathologist. But he’s not calculated and methodical enough to be a Patrick Bateman. At one point, David alerts Michael to the ruse because he doesn’t know how to turn off a Palm Pre. He’s not brutal enough to be a Michael Meyers. Throwing an old lady down the stairs doesn’t quite do it. Hell, he’s not even suave enough to be Ted Bundy — “Boys will be boys?” That’s your pickup line?

Instead, you’re presented with a serial killer who is nothing more than a stay-at-home carpenter whose approach to family disputes is to spaz out, pack up his knives and mallets and find another family who will “make it work.” He’s just a mopey loser who happens to also kill people.

But if the serial killer’s wimpiness is disappointing, the other characters are just annoying. The normally charming Ward comes off as a vapid MILF cheerleader as Susan, hanging on David like some sort of virginal poodle-skirt-wearing 16-year-old. David quits his job, hides from her friends and chokes their son. Her response? “I don’t care, I love him!”

And then we have our protagonist. Michael’s an angry young teen who’s not particularly angry about anything. He puts headphones on, cries and swims. That’s literally half of his action in this movie. And except for one scene, his girlfriend Kelly (Amber Heard) is never fully clothed. That’s because it was raining. While Michael is probably the least predictable of the characters, it’s only a difference between whether he’ll smile or mumble.

But this film, despite its half-hearted characters, isn’t a total wash. The tension may be a little drawn out over the course of its hour-and-40 minute run time, but there are flashes of creativity. The camerawork in periods of relative calm has a rather eerie and isolated feel to it; when Kelly and Michael discuss David’s secrets, the camera focuses on the two floating on parallel floats in a calm pool, spinning as they hold on to each other. Had there been a consistent cinematic theme throughout, the film could have more than made up for the wasted actors.

Unfortunately, what we’re left with here is just mediocre. A few thrills here, a few expected but delayed deaths and a long game of cat and mouse between the son and stepfather. And even that ends with a rather dampened thud and a fat Michael (That’s right, where’s your shirtless stud now?).

Oh, well. They can’t all be winners.

2 1/2 stars out of 5.