It is a stormy desert night. Business has been lousy at Al's, an isolated roadside diner near Groom Lake Air Force Base. AL, the owner and cook, decides to close up for the night. He sends his "been there, seen it all" waitress LOU home. His only customer, MICHELLE, a part-time hooker, unhappily realizes she will have to trade Al sex for a ride home.
As Al tries to collect the "fare," Lou returns with customers driven to Al's by the storm: PETE and MARIA LANGELLA (a bickering couple), OLEG and IVANA, (Russian-accented "French" tourists), GUSTAVE and FLOWER (a beatnik couple), HUNTER (a Jag-driving Vegas highroller) and BITSY (his "girlfriend"). Into this brew arrives Captain "HAP" BEAUMONT, the new base commander and his wife MARILYN, dust-covered from walking through the storm after their car was run off the road by a speeding Jag. Hap socks Hunter upon discovering he was the Jag driver.
As everyone waits out the storm, rumors about nearby Area 51 surface. Gustave and Flower turn out to be government conspiracy nuts, convinced aliens are being kept at Area 51. Oleg and Ivana seem overly interested in information about the base. Maria believes in UFOs while husband Pete is a complete skeptic. Hunter is anxious to leave for an "important business meeting" in Vegas, while Bitsy is concerned about Michelle's not-so-subtle overtures towards Hunter.
Hunter discovers BILLY, an A.W.O.L. G.I., trying to steal his Jaguar. Billy explains that something weird is going on at the base. "People aren't themselves." When the BASE M.P.s arrive, Billy tries to escape and is shot down. The M.P.s restrict everyone to Al's diner as they drag Billy away.
Hunter, Bitsy, and Michelle try to make a break for it, only to discover they can't leave the parking lot. An invisible field has trapped them in the diner. Tensions and suspicions ratchet up. Suddenly, the people trapped in the diner begin revealing who they really are...