The rare sequel that improves upon its predecessor and corrects many, if not quite all, of that movie's problem areas, "Saw II" may have been rushed into production—it is coming out exactly a year after the release of 2004's indie hit "Saw"—but it doesn't show. Held together by a well-crafted screenplay by Darren Lynn Bousman (also making his feature directing debut) and Leigh Whannell, "Saw II" has upped the ante in not only violence, blood and number of victims, but also in rattling intensity. Gone is the pointless Danny Glover subplot that got in the way of the main story and severely damaged the outcome. Gone are the messily constructed flashbacks and flashbacks within flashbacks. And gone is the twist ending so contrived that it stopped making a lick of sense after one second's thought about it. There are likewise some major surprises at the end of "Saw II," but this time they hold a certain amount of logic and stand up to scrutiny.

Set very shortly after the events of the original picture, "Saw II" jumps right into the ongoing investigation of the Jigsaw Killer (Tobin Bell) by police detectives Eric Matthews (Donnie Wahlberg) and Kerry (Dina Meyer). Finally capturing the cancer-stricken Jigsaw in his hideout, Matthews is soon horrified to discover a series of set-up monitors capturing eight strangers—including his own teenage son, Daniel (Erik Knudsen)—trapped in an unknown house. A toxic nerve gas is being leaked through the building's vents that will kill them in exactly two hours. Their only hope for survival is to play by Jigsaw's deadly games, forced to the extremes of human endurance and sacrifice in exchange for antidotes that have been hidden around the house. If they fail to succeed, they die. As Matthews questions Jigsaw and attempts to drive his son's whereabouts out of him, the kidnapped group begin a fight for their lives as they grow sicker by the minute.

Not for the weak of stomachs, "Saw II" is the type of grisly, no-holds-barred horror show that doesn't frighten so much as it profoundly unsettles. The stand-alone pre-title sequence depicting one of Jigsaw's games in motion—a man is stuck in a venus flytrap contraption that will smash his skull if he does not cut his own eyeball out to reach a surgically placed key—is so visceral and disturbing it had me wriggling in my seat and holding my hands up at my face. A film hasn't inspired such a reaction in me since Johnny Knoxville and gang gave themselves paper cuts in 2002's "Jackass." A close second prize for most effective, icky, and ingeniously wicked moment involves a pit of syringes and a buried key. "Saw" was more atmospheric and traditionally scary, but it also treaded through too much needless exposition that buried the good stuff. By comparison, "Saw II" gets the heart racing in a way the original never did and, save for a couple too many returns to the police procedural side plot, is leaner, faster, and more involving.

A largely unseen presence in the first film, Jigsaw's identity is out in the open here, and he is more of a lead character. While this was cause for some initial pause, his development ultimately aids in giving the film a deeper subtext. A man practically on his deathbed, Jigsaw's goal is to seek out wrongdoers whom he believes do not value their lives and put them to a test to see how far they will go in order to spare themselves. This was touched upon in "Saw," but is explored to a larger extent this time and gives the viewer something to think and debate about in between the bloodletting. Tobin Bell is genuinely memorable and creepy as The Jigsaw Killer, giving him a calm, collected demeanor that would almost appear to be clear-minded if he wasn't so psychotically deranged. He's the 21st century's answer to Hannibal Lecter, and doesn't have to lay a hand on anyone for them to befall gruesome fates.

The rest of the ensemble are solid, too, with Shawnee Smith (2004's "A Slipping-Down Life") strongly reprising her role as Amanda, the only past survivor of Jigsaw who finds herself once again captive inside the house. As Det. Eric Matthews, Donnie Wahlberg (2003's "Dreamcatcher") again proves to be every bit the talent as brother Mark, if not more; he is compelling to watch as he tries to turn the tables on Jigsaw in order to find his son before it is too late. And Beverley Mitchell—a long way from her role as Lucy Camden on TV's long-running "7th Heaven"—is touching as the most vulnerable of Jigsaw's possible victims, Laura, painting the picture's most realistic and humane portrait. Not much is learned about Laura's background, and yet Mitchell gives her a quiet sense of dread and regret as she recognizes her impending doom while those around her are too busy arguing with one another. Added digging into what these eight strangers' dark pasts hold to lead them to their present situation could have been beneficial in making them more rounded and sympathetic. As is, they are mostly one-dimensional chopping blocks at the mercy of Jigsaw's devious games.

"Saw II" has its share of problems—the entire premise copies off of the more inventive "Cube" and doesn't take advantage of as many individual trap situations as it should have—but it is a step in the right direction for a flourishing genre series that will no doubt see a third chapter within the next year or two. Pleasingly, the freaky decapitated sow head makes a cameo, while the use of the talking clown puppet once again seems like an unsuccessful gimmick but wisely disappears after the first half-hour. "Saw II" is pitch-black, ugly, and stomach-churning in spots, but those are precisely the characteristics director Darren Lynn Bousman was shooting for. And the ending, building one twist and revelation upon another, craftily comes full-circle with the original "Saw," making a fresh viewing of that one worthwhile before seeing the sequel. Rough around the edges, but knowing how to ratchet up distinct feelings of tense giddiness and extreme apprehension, "Saw II" is an exploitation flick with style and skill to go along with its stream of red stuff.