Harry Potter never drove a Gremlin, but as an accused murderer in “Horns,” Daniel Radcliffe must maneuver his way through a script that goes just about nowhere. (Doane Gregory/RADiUS-TWC)

The snippet of pillow talk between canoodling lovers that opens “Horns” — “Are you horny?” “I’m getting warmer.” — would be unremarkable, were it not for the fact that the hot-and-heavy exchange quickly becomes the last subtle thing about the film, which manages to simultaneously overtell and underserve the story of Ig Perrish (Daniel Radcliffe), a man who sprouts a pair of devil’s horns after he is accused of his girlfriend’s murder.

The ramlike protuberances that suddenly erupt from Ig’s forehead (a physical metaphor for the way he has been demonized by his friends and neighbors) are only part of the film’s heavy-handed approach to storytelling. Images of flames and devilry abound in a movie whose art direction seems to have been inspired by Dante’s “Inferno” — the graphic novel version. (In point of fact, the movie is based on a 2010 book by Joe Hill, the son of horror writer Stephen King.)

Perhaps most tellingly, Ig tools around town in a fire-engine-red AMC Gremlin.

Naturally, our hero claims he did not murder his longtime sweetheart, Merrin (Juno Temple), who coincidentally shares a name with the title character of “The Exorcist.” On one level, “Horns” is a fairly straightforward if uninspired mystery about a man trying to clear his name. What makes it different is that Ig’s strange condition suddenly makes all the people in town unable to suppress their deepest, darkest secrets in his presence. Looking like the devil, so to speak, has its advantages: It helps Ig in his investigation.

This should have been the best thing about the film. Unfortunately, as imagined by playwright and television scribe Keith Bunin (“In Treatment”), who adapted Hill’s book, most characters’ taboos involve sex, and not even the especially imaginative kind. It’s like “Liar Liar” in reverse: In “Horns,” everyone but the main character has to tell the truth, but the truth just isn’t all that interesting. Radcliffe is at least watchable. His film career of late (“The Woman in Black,” “Kill Your Darlings”) has been bold, making memories of Harry Potter fade by the minute.

Even with his special power over people, it takes Ig a while to get to the bottom of the crime, and only partly because he’s not 100 percent sure that he didn’t kill Merrin himself. He was drunk the night it happened, and he was upset after she dumped him, in a scene that takes place at Eve’s Family Diner (a restaurant whose logo is an apple — get it?).

Sure enough, serpents will soon be slithering all over the place, too. And one character, Ig’s lawyer (Max Minghella), is missing the two middle fingers of one hand, the result of a childhood accident that makes it easy for him to form the “horns” gesture associated with Satanism (or, perhaps just as plausibly, the University of Texas).

Metaphorically, director Alexandre Aja (“The Hills Have Eyes”) pulls out all the stops, throwing every hellish allusion he can think of at the screen and hoping that one of them sticks.

The damned thing is, there doesn’t seem to be any larger point to all of this hellishness. Guilty or innocent, Ig doesn’t really represent anything except a dude with horns. And the film has nothing to say about human nature, at least not that hasn’t been said before, and more poetically.

Heedless of purpose, “Horns” charges full speed ahead anyway, ramming its high-concept hooey down your throat until the only heat you feel is from indigestion.

½

R. At area theaters. Contains obscenity, violence, sex, nudity and drug use. 120 minutes.