How's this for a really inspired and effective handy-dandy sci-fi/horror combo premise: Let's take your basic randomly selected motley assortment of everyday folks gathered together in a deep, isolated, self-contained underground nuclear fall-out shelter so they can survive an impending end-of-the-world holocaust tale and embellish on this standard situation with a borrowing from the then hip killer-animals-run-amuck trend by having a horde of vicious, relentless, chattering vampire bats with a taste for human blood attack the understandably terrified bunch at regular bloodcurdling intervals. Sounds like a pretty desperately reaching "high concept" effort, right? Well, that brusque blow-off assumption is wrong. Dead wrong.<br /><br />Under episodic TV show vet Sutton Roley's taut, capable direction the admittedly threadbare story works surprisingly well, resulting in a genuinely scary, creepy and suspenseful nail-biter. The neatly varied cast helps a lot; they fill out their stock roles with commendable conviction. Former child actor Jackie Cooper portrays a cross, feet-of-clay rich jerk grumbler with stand-out sliminess. Constantly reliable B-pic perennials Richard Jaeckel (who later had a fatal run-in with a killer bear in "Grizzly" and got offed by a pack of wild dogs in "Day of the Animals") and Alex Cord (the latter bears a passing resemblance to tough guy thesp extraordinaire William Smith here) make for properly stalwart heroes. The always composed and elegant Diana Muldaur brings a welcome touch of class to the tense, grisly proceedings. Future "Hill Street Blues" regular Barbara Babcock is a lovely damsel in distress. A bespectacled Bradford Dillman (who went on to get stung to death by killer bees in "The Swarm" and had his face nibbled on by carnivorous fish in "Piranha") nerds it up nicely as a duplicitous dweeby scientist. Chronically unsung character actors Pedro Armendariz, Jr. and Lincoln Kilpatrick contribute solid performances as an eminently expendable decent dude and a gallant, rugged Olympic athlete, respectively. The sequence where Kilpatrick tries to climb out of the subterranean shelter on a rope is both gripping and nerve-wracking. The bat attacks are almost unbearably frightening and ferocious. The claustrophobic set design, Gabriel Torres' cramped, closed-in cinematography, Fred Karlin's jazzy, spooky score, the unremittingly eerie tone, and the bleakly ironic ending all add considerably to the gut-wrenching tension. And those nasty screeching bats are truly horrifying little suckers!