If you’re going to make a movie that’s frankly ridiculous, the worst thing you can do is be timid about it. A lot of sci-fi and fantasy films are built on “Aw, come on now”-worthy premises, but if you charge forward with enough energy and attitude, you can roll right over the viewer’s suspension of disbelief. A great example is last year’s wildly under-appreciated The Warrior’s Way, which piled one crazy idea on another and gave them plenty of room to bounce off against each other as they cohered into gloriously absurd and rewarding entertainment. The greatest failing of I Am Number Four, the screen adaptation of Pittacus Lore's sci-fi novel, is that it keeps threatening to get full-on ridiculous, yet doesn’t actually do so until the last act, when it’s really too late to save the day. Most of the time, I Am Number Four doesn’t know if it wants to be a young-adult War of the Worlds or a big-screen version of Dawson’s Creek about the new kid who’s really from out of town; most of the time it leans to the latter, which in this case was not a good choice. I Am Number Four stars Alex Pettyfer as John Smith, who has just moved to Paradise, OH, from New Mexico with his dad, Henry (Timothy Olyphant). Or at least that’s what his new classmates at school think; actually, John is one of the last of the Lorians -- survivors of an alien civilization who are in hiding on Earth from the Mogadorians, their arch enemies who act like the meth-crazed school bullies of the universe. John just wants to blend in and not call attention to himself, which is just what his guardian Henry wants, since there are Mogadorians in the United States looking for them. But almost without trying, Alex gets on the wrong side of Mark (Jake Abel), the arrogant and short-tempered captain of the football team, when he befriends Sam (Callan McAuliffe), a nerdy kid obsessed with UFOs and ancient astronauts, and falls for Sarah (Dianna Agron), a pretty girl with an artsy bent who used to date Mark. Like his fellow Lorians, John has some pretty impressive superpowers, and while trying to protect Sarah from Mark, he ends up tipping his hand and revealing his true nature, not long after we learn that Sam’s dad was abducted by aliens and may be unwittingly luring the Mogadorians to Paradise. In its final reels, I Am Number Four dramatically shifts gears and transforms itself into a slam-bang sci-fi action epic overloaded with special effects and full of battles between various all-powerful folks from other worlds, and if it’s way over the top, it’s also fun and doesn’t skimp on imagination and interstellar fisticuffs. The trouble is, by the time I Am Number Four summons up the courage to get full-on ridiculous, it’s too late -- the movie has spent so long dealing with John’s teen angst and his played-cute romance with Sarah that the narrative has fallen into a coma, and even the closing fireworks can’t rouse it. Most of the time, I Am Number Four plays more like a pilot for some basic-cable TV series about winsome teens in the Midwest than a sci-fi thriller, and while both Alex Pettyfer and Dianna Agron are both appropriately teen-star pretty, neither of them has the charisma or imagination to make their characters worth caring about after they’ve been together onscreen for a few minutes. Jake Abel is more effective as the jock/bully who seems almost as threatening as the Mogadorians, but he has only one move in his dramatic arsenal and it wears out long before the movie ends. Callan McAuliffe is believable as the target of Mark’s sadistic pranks, though he’s also annoying enough that it’s easy to see why everyone picks on him. And while Teresa Palmer is fun, spunky, and kicks serious butt in the finale as another Lorian exile, she also seems to have dropped into I Am Number Four by accident from another, significantly more entertaining movie. Of course, the cast can only do so much with what they’re given, and the screenplay by Alfred Gough, Miles Millar, and Marti Noxon (adapted from a novel co-written by James Frey, who has embraced a pseudonym and young-adult fiction after suffering the Wrath of Oprah) is blah and full of cliches, and can’t conjure up much of a reason why the Mogadorians are out to take over the universe beyond simply being a bunch of meanies (and even if they are the bad guys, they seem to be having a lot more fun than most anyone else in this movie). And director D.J. Caruso (who, as the auteur behind Disturbia and Eagle Eye, is an expert at directing Shia LaBeouf, if nothing else) is inconsistent with his pacing, doesn’t draw much from his cast, and drains the bulk of the movie of any emotional energy. Even though I Am Number Four rallies for a big finish, it almost seems as if we’re watching another story when the big battle and a really teed-off Mogadorian critter finally pump some adrenaline into this picture. Better to wait until this shows up on DVD or Blu-ray so you can jump to the big stuff at the end rather than sitting through the dross that sets it up.