The makers of “City by the Sea” must have very little faith in their viewers’ intelligence. Not only do they play their story, about a cop confronted by the fact that his estranged son is the chief suspect in a homicide case, at a nearly funereal pace, endlessly hammering home the same points as though the audience were too dense to comprehend them without constant repetition; they also pass up no opportunity–from allusions in the dialogue to ocean-view vistas to banners floating from telephone poles–to remind us of the picture’s title. Perhaps director Michael Caton-Jones and his cohorts were afraid that we might forget what movie we’re watching upon awakening from one of the brief naps their work is liable to induce, and are helpfully encouraging us to remember something which, unfortunately, we’d probably prefer to forget. But they would have been better off just letting us snooze in peace; “City” is a slow, soggy, soporific, visually dank crime melodrama/character study that would be more at home on the small screen if it weren’t for its stellar cast.

Ken Hixon’s earnest but earthbound script is based–rather loosely, one suspects–on one of those implausible true crime stories that often become the stuff of magazine articles (in this case one by Michael McAlary called “Mark of a Murderer,” which appeared in Esquire in 1997). Robert De Niro plays Vincent LaMarca, a NYC homicide detective who, along with his chubby, lovable partner Reg (George Dzundza), is assigned a case involving a corpse that’s washed ashore in Brooklyn. There’s no mystery about the perpetrator–we’ve already been shown a scruffy young druggie called Joey (James Franco) stab the victim, a bellicose dealer named Picasso, and toss the body into the drink–but as the investigation moves to the disintegrating community of Long Beach on Long Island, where LaMarca grew up, it’s soon revealed that Joey is his own boy, whom he left behind with his ex-wife when they divorced years ago and hasn’t seen since. LaMarca, of course, tries to make up for his past neglect (and, as it happens, for a “sin of the father” that goes back to a still earlier generation) by getting his son safely into custody– something that becomes more difficult when tragedy strikes after he’s removed from the case and his partner takes over solo. (The casting of Dzundza as Reg, and Vincent’s early references to the fat fellow’s happy homelife, will surely be enough to tell you in what that tragedy consists.)

Much of this may be based on fact, but in the telling it comes across as contrived and unlikely, and matters are made worse by further additions. LaMarca is given a sort-of girlfriend, a likable upstairs neighbor who’s surprised by all the revelations concerning his past (an obvious surrogate for the viewer); the great Frances McDormand is utterly wasted in the thankless role. Joey is provided with a girl of his own, Gina (Eliza Dushku), and with a sweet little son to boot. Meanwhile a tired subplot proceeds involving Spyder, the sleazy boss of the dealer Joey offed; this character is played by the scowling William Forsythe, who looks positively absurd perched atop a motorcycle with long locks billowing in the breeze. (As if a Spyder weren’t enough, there’s another character called Snake, the sniveling buddy of Joey who gets him into trouble in the first place. Brian Tarantina plays him, badly, as a collection of nervous ticks.) Meanwhile Franco sulks around in a vain attempt to channel the spirit of James Dean, whom he once portrayed in a television movie. Charismatic he’s not, especially in his ragged stocking cap.

And what does De Niro bring to this all-too-somber party? Not much, unhappily. This is one of those roles in which he underplays in an effort to come across as an ordinary Joe, and as usual in such parts he’s oddly slack and boring, an occasional odd glance and peculiar line reading apart. The sole thing at all different this time around is that his hair is slightly longer than is customary, and that’s hardly enough of a distinction to make playing the role worthwhile for him or watching it enjoyable for us.

As if all this weren’t bad enough, the Long Beach setting of the picture (actually shot in Asbury Park, New Jersey) is unrelievedly gloomy and depressing. In that respect, at least, “City by the Sea” will accurately reflect the likely mood of its unhappy audiences. Where’s all that ocean erosion when you really need it?