You really have to hand it to “Gnaw: Food of the Gods II.” Most giant-rat movies would be content to feature a handful of people being chewed to death by radioactive rodents and call it a day. But “Gnaw” is one of those B-movies that uses its monsters merely as a starting-off point and builds from there. Yes, plenty of giant rats nibble on plenty of throats, but that doesn’t include the amoral scientist who is turned into walking cream of mushroom soup, the dream sequence where the hero turns into a giant while having sex, the synchronized swim meet that turns into a literal bloodbath or the 10-foot-tall 10-year-old who kicks off the movie’s plot.

The best place to begin talking about “Gnaw” is its hero, an unusually buff geneticist who is trying to find a cure for an experimental growth hormone used by one of his colleagues. The hormone is responsible for the gigantic fourth-grader’s unnatural size and aggression. (“I’d like you to meet my colleague,” the kid’s doctor says. “I’d like you to get the fuck out of my room!” the kid retorts.) Our hero, Neil, takes the hormone back to the lab, where he does science in a montage that feels like a training montage from a karate movie. Neil gets so STOKED about science that he even gives an enthusiastic fist pump at his computer.

Trouble arrives when a group of student animal rights activists break into the lab one night and start smashing up the place, which inadvertently exposes a bunch of lab rats to the hormone. Now there are giant rats loose on campus and Neil has to convince the university’s stuffy dean that the roided-up rodents are an actual problem while attempting to put a stop to the menace altogether.

“Gnaw” accomplishes the feat of being formulaic without being predictable. For instance, you could probably guess that some of the rats’ victims will be a couple of horny college students. What you wouldn’t be able to predict, however, is that one of them would be chased across the quad with his pants around his ankles and that you’d get a rat’s-eye-view of his naked ass for more than one shot. You could figure out that the sneering scientist who wants to get rich off the growth hormone won’t survive the movie. Would you believe that he would die not by rat attack, but by accidentally turning himself into a man-sized cluster of oozing tumors? Unlike a lot of killer-animal movies, “Gnaw” is smart enough to understand that a horror movie cannot live by giant rats alone, especially when you’re making a sequel to a giant rat movie in the first place.

And that’s a good thing, because the giant rats themselves are not especially interesting or scary. Watching “Gnaw” reminded me at times a lot of “Night of the Lepus,” the infamous 1970s ecological disaster flick that tried to evoke terror with a rampaging herd of giant bunnies. “Gnaw” also uses a combination of life-sized puppets and real animals shot against miniature sets to achieve the effect of giant animals on the loose, but “Gnaw” doesn’t attempt to compensate for the rats’ quick movements by using slow-motion photography the way “Night of the Lepus” did. Slowing the film down just a bit would have helped sell the illusion that these are Volkswagen-sized vermin and not just pet-store rats scampering over dollhouse furniture. The real-life rats are also impeccably groomed, their fur glossy and straight in a way that no rat that just crawled through five miles of sewers could ever hope to achieve. Maybe the growth formula contains Pantene Pro-V?

The apex of the rats-in-a-dollhouse aesthetic comes during the final sequence, during the doomed swim meet. The rats burrow their way through the bottom of the pool and start chomping on the swimmers before turning their attention to the panicky spectators. This leads to some amazing stuff, like the guy who freaks out, swipes a gun from a cop, and just starts pumping lead in all directions. I don’t think he hits a single rat, but he does kill three or four people before another guy wrestles him to the ground. Then there’s the little kid who hides under the bleachers and finds Neil’s favorite white rat, now the size of a hatchback, waiting under there for him. The dipstick dean is chased to the top of the high dive by a rat and, wouldn’t you know it, he manages to miss the pool.

Neil arrives with a flute and herds the rats into a plaza outside the natatorium, but the SWAT team is ready for them and they massacre the mammoth Mickey Mouse Club with machine-gun fire. This apparently wasn’t part of Neil’s plan, because he starts screaming for the cops to stop shooting. At this point I’m still kind of sympathetic to Neil because I know those rats were like family to him but still, buddy, they’re giant rats who now have a taste for human flesh. Maybe if you had tried the Pied Piper thing sooner than in the last 10 minutes of the movie none of this would have been necessary. But just when you think they’re going to end this movie on a shot of the hero crying over a pile of giant rat carcasses, “Gnaw” pulls one more ace out of its sleeve, and in my opinion it’s one of the most tragic missed opportunities in schlock history. Neil gets a call from his colleague from earlier in the movie. The giant kid from the start of the movie is loose, and we see her get her neck snapped by a giant rubbery hand. The end? If only we could have seen “Food of the Gods III” with that giant kid breaking necks and cursing like a sailor the whole time! When will Hollywood finally get the guts to make a giant-killer-child movie? If 12 years can go by between “Food of the Gods” and “Food of the Gods II,” certainly 27 years isn’t too long to wait for the third one.

The difference between good schlock and bad schlock is the good stuff keeps doubling-down because it knows it has to keep moving or the audience is going to get bored. No one cares if Neil can talk the dean into believing him about the giant rats – that’s just connective tissue that gives us a reason to root for the rats to nibble out the dean’s spine. As avatar of the drive-in Joe Bob Briggs so often put it, movies like “Gnaw” are great because they “don’t have any story to get in the way of the plot.”

Special Guest Appearance by the special effects guy working the goo plungers down in the corner.