"Somewhere along the way I lost a step," says Vin Diesel, aka that gravelly voiced, visually impaired, planet-hopping outlaw and badass they call Riddick. "I went and got sloppy."

He’s talking about how he ended up on a desolate planet facing murderous canine creatures and giant deadly serpents. But he could just as easily be talking about the lethally inadequate screenplay he’s up against. "Sloppy" is a kind word, actually, for the ridiculously clumsy dialogue in "Riddick," the third and latest installment of the sci-fi saga.

‘RIDDICK’ Rated: R Opens today

Of course, none of this will likely matter to the hard-core fans who’ve been waiting for this movie since 2004’s "Chronicles of Riddick," a successor to 2000’s "Pitch Black." Even though that megabudget film tanked at the box office, it fed the franchise’s avid cult following, as have a pair of video games.

And fans will no doubt be especially happy that in "Riddick" — its title now streamlined, along with its budget — no compromises have been made for a wimpy PG-13 rating. No, it’s an R this time, which allows for a few characters to meet a particularly gory end (don’t run out for popcorn during the second half!), not to mention freewheeling profanity and one gratuitous nude scene.

Not all is bleak. The bald and beefy Diesel, whose sturdy commercial appeal is proved again and again with the huge success of the "Fast & Furious" franchise, is always fun to watch. But his presence alone, comfortably durable as it is, can’t make up for the total lack of other interesting characters in the screenplay by David Twohy, who also directs. Alas, that includes Katee Sackhoff as the lone female, a feisty bounty hunter named Dahl. The name sounds exactly like "doll," which is basically her role; she’s pretty but has no interesting back story or dialogue, save one profane comeback sure to draw hearty cheers.

If you didn’t see "The Chronicles of Riddick" — or if you saw it and didn’t quite follow the overwrought plot — you’ll be OK here, because only brief references are made to Riddick’s checkered past. A quick flashback reminds us that when we last saw him, he’d been crowned the Lord Marshal of those dark Necromongers. But hey, the grass is always greener in outer space, and what Riddick really wants is to return to his home world, Furya.

So he makes a deal with his enemy, Vaako (Karl Urban, appearing here for a few seconds). But that’s where he’s become sloppy. He’s duped — dropped onto a desolate, dangerous place called, well, Not Furya. He’s badly wounded, too. And then there are those vicious dogs, and those scary serpent creatures.

But this is Riddick, and somehow, he makes his way to an abandoned mercenary post and sends out an emergency signal. His plan is to escape on the ship of the bounty hunters sure to arrive any minute.

And arrive they do — two competing bands of them. One is led by the almost comically inept Santana (Jordi Molla), who’s intent on beheading Riddick, and has brought a box along for that purpose. The bounty, you see, is doubled if Riddick is brought back dead.

But Boss Johns (a square-jawed Matt Nable) has other ideas. He’s the head of the other band, and he has some important questions for Riddick — preferably to be answered while that shiny bald head remains in place.

Will Riddick, as always a one-man army, somehow survive? "I don’t know how many times I’ve been crossed off the list and left for dead," he says at one point. "This ain’t nothing new." Like the character, this franchise may yet rise again, but let’s hope that next time, the filmmakers do bring something new.