In Secret Window, Johnny Depp’s hair is as great a presence in it as the quirky mannerisms that are his registered trademark.

Whenever Depp’s struggling writer Mort Rainey awakes from a couch nap, his hair is a mussed-up masterpiece, bad highlights and all. Mort’s hair is messy, but styled to be that way. The movie he’s a character is styled to be clever, but it’s just a mess.

Secret Window isn’t a Stephen King-based stinker on the order of Dreamcatcher, but it’s a thriller that’s oafishly obvious from the moment things might not be what they seem.

For Depp, it’s yet another recent case of good performance, awful movie in a film where he’s the star (Pirates of the Caribbean and Sleepy Hollow excepted). Maybe it’s a selfishly shrewd move on Depp’s part, knowing if the movie’s a dog, people will no doubt say he was the best thing in it.

That’s certainly the case here, as Mort’s bitter, disaffected sarcasm, scaredy-pants twitches and laugh-out-loud dishevelment are the film’s sole saving graces. He’s a mystery writer, recently cuckolded by his wife (Maria Bello) and condemned to a life of Doritos and Dew in a woodsy cabin.

Mort’s goal isn’t so writing as it is to not spend the day in his ratty bathrobe. But he’s jolted into a story from his past with the arrival of John Shooter (John Turturro, whose Southern drawl redefines cornpone menace).

Shooter accuses Mort of plagiarizing one of his stories, demanding Mort rewrite it with Shooter’s original ending and publish it under Shooter’s name. Strange coincidences prevent Mort from getting a crucial copy of Ellery Queen’s Mystery Magazine, which would prove he wrote his story before Shooter.

But then bodies start piling up and so does the ridiculousness in writer-director David Koepp’s film, easily the flimsiest story this scribe has ever hung a hook on. It doesn’t help that King, sadly descending into self-parody as he ages, seems hung up on his own bad motifs such as the deceptively naïve lawman.

King is capable of great character moments and comedic beats, which we get early with Mort, namely when he chides Shooter’s accent and taunts Ted (an underused Timothy Hutton), his wife’s new lover.

Still, the movie can only skate so far on Depp’s charisma and a handful of gleefully bent internal monologues. Unlike other easily pegged movies such as Matchstick Men or Identity, Secret Window has no fun in winding to its conclusion.

From his Spider-Man adaptation, Koepp lifts nearly verbatim for Depp a scene done better by Willem Dafoe and, of all things, tosses in a from-nowhere miscarriage reference. Worse yet, it belabors its “twist” with an overcooked, overlong third act.

Early in the film, Shooter can’t decide what was worse — Mort’s stealing his story or ruining his ending. Depp does all he can to steal the movie, but it can’t save an outcome that is all but ruined from the start.