This speculative horror film details the tribulations endured by a specially-selected test group of 11 people who are informed that they will be the only occupants of a nuclear fallout shelter built half a mile below the Earth's surface. Chosen by project coordinator Peter Macomber (Bradford Dillman) as a fair cross-section of humanity, the group includes a politician, a businessman, an athlete and an author. As it turns out, the "survivors" are unwitting participants in one of those contrived psychological experiments featured so often on programs like The Twilight Zone. To make matters worse, someone's left a vent open, releasing thousands of ravenous vampire bats. Produced in Mexico, this tepid psycho-thriller plays out like the aforementioned TV drama, albeit padded out to 100 minutes. Said padding seems comprised of equal parts dull dialogue and interminable battles with the winged foes -- which are admittedly quite realistic and make for some genuine creep-out scenes.