Although it’s ambiguous about much, Martin Scorsese’s Shutter Island makes two things extremely clear: Leonardo DiCaprio is a seriously big movie star, and delivering on genre expectations excuses a multitude of sins as far as audiences are concerned.

The Scorsese-directed suspense-horror film has been number one at the U.S box office for two consecutive weekends, despite its stunning  collection of genre cliches, long-out-of-fashion narrative ambiguity, agonizingly slow pace, and few real surprises, along with the director’s usual arresting visual style. Thus a good deal of the credit must go to DiCaprio’s star power.

Telling the tale of a U.S. Marshall, played by DiCaprio, who with his new partner investigates the escape of a violent prisoner/patient at a federal detention and treatment facility on an island several miles off the coast of Massachusetts, Shutter Island employs enough horror and suspense cliches to scare off any discerning moviegoer.

There are, for example, the isolated island itself (so reminiscent of Agatha Christie’s And Then There Were None and many other suspense stories), a stormy scene in a graveyard, wanderings through a confusing maze of corridors in an insane asylum, the hardnosed detective investigating a case that becomes much more complex than he thought it would, a sinister ex-Nazi, a character’s disturbing memories of wartime, classical music backing a scene revealing atrocities, weird people making perplexing claims, a character taking a hypodermic away from a doctor and injecting the latter, an automobile explosion, and many, many more.

What’s more, Scorsese employs this farrago of the familiar in the service of a plot that ultimately becomes one of those “what really happened?” stories that were so popular in the late 1960s and early ’70s and then died an extremely well-deserved death. Scorsese and his screenwriters actually do a good job of bringing out the epistemological implications of this material, which could inspire in more-educated audience members a few moments of consideration about how humans can in fact know that we know things. But surely no more than a few moments of it.

Unfortunately, the film is so resolutely irresolute that it’s ultimately impossible to know what really happened, and the characters are too wooden for us really to care. DiCaprio’s U.S. Marshall, for example, is given a huge amount of back story in the film, yet the narrative’s ultimate undermining of the audience’s knowledge of what happened and what he actually did makes it impossible for us to judge his actions and thus know how much to sympathize with him. We know little about him except for the tragedies he has endured, which are revealed in only rather piecemeal fashion during an overly drawn-out narrative.

This seems to be a choice on the director’s part, apparently in hopes of making the atmosphere that much creepier. The Dennis Lehane novel on which the film is based reportedly includes a good deal of lighthearted byplay between the marshall and his partner, and it seems a rather better choice than Scorsese’s.

Thus, despite DiCaprio’s star power, he is never able to make the character particularly likable, further undermining any change at audience sympathy.

All of this makes it even more impressive that audiences are turning out in relatively big numbers. To be sure, a good many people who have seen Shutter Island seem quite convinced that it is a mystery meant to have a real answer, as exemplified by a discussion at Nonetheless, it seems quite clear that Scorsese and his writers intended that no definitive answer to the film’s central mystery should be found within its story.

It’s possible, of course, that some ticket-buyers may well be attracted by the film’s narrative ambiguity, or that some were drawn in by a fondness for Lehane’s novel (but not many, I think). Perhaps the couple of decades of blessed freedom from these ambiguity stories has allowed the arising of a new generation of moviegoers not yet turned off by such stories. Amybe this sort of story is no longer a cliche for a large part of the audience.

The trailers, commercials, and other advance publicity for the film, however, certainly did not emphasize the presence of such ambiguity. Instead they dwelt on the presence of DiCaprio, Scorsese’s visual bravura, and the picture’s gothic atmospherics. In other words, a big star in a genre film.

My guess is that Hollywood industry insiders won’t find Shutter Island ambiguous at all. The message is clear: big star plus recognizable genre equals serious money. That’s the kind of message movie Hollywood does best.