There is a certain subgenre of sci-fi horror. A group of scientists and military are isolated in an underground (or outer space) facility. An alien or monster or android goes on a killing spree. The people bicker, and flirt, and gripe, then skulk off into darkened corridors for the monster to pick them off. Shadowzone and Xtro II: The Second Encounter are two such films. The Area 51 Incident is yet another.

Doug (Toby Wynn-Davies) is head scientist at Area 51. He's investigating a space portal that leads to a planet several hundred light years away. That's why Area 51 was built at its location.

I'm not sure where that is. The film's marketing claims it's at "the infamous Area 51." An early scene does indeed say "Area 51." Yet everyone has a thick British accent. Doug refers to "Unit 51" and then later to "the British Area 51." Later, a radio news reporter says that creatures are overrunning "the state." I don't think Britain has "states," so are we in the U.S.?

Perhaps the producers weren't sure whether to set the film in the U.S. (with its "famous" Area 51), or, because of all the accents, just fess up that we're in Britain. And maybe they kept changing their minds, and rewriting the script, during filming.

Anyway, tonight's the night that Doug's scientist son Trent (Scott Jeffrey), and scientist Jenny (Megan Purvis), come to visit. It's also the night the portal is finally opened.

A half dozen people in white lab coats, and a half dozen in camouflage and holding guns, stand about the lab. What the armed soldiers are for, I don't know. I never see them guarding labs in science documentaries, but they're always there in horror films. Like they know they're in a horror film.

Not that it helps. Once the portal opens, hundreds of CGI monsters, looking vaguely like the spawn of a dinosaur and the creature from Alien, rush out and chomp down the humans. No curiosity, no attempts to communicate or form cultural exchanges. Damn aliens.

Pretty much everyone dies, aside from our three heroes, who escape to an underground military base. They pick up three nightclub patrons along the way. One of them is already infected by the alien.

Yes, like the creature in Alien, these monsters reproduce by inserting their -- eggs? -- into the mouths of humans. No elaborate facial grasp. Being low-budget aliens, they merely vomit red bile into their victims' mouths. (However did they reproduce before they had a space portal to Earth? Which they apparently built, though they carry no technology on their naked, scaly green bodies.)

The military base has all of three soldiers, slovenly and unkempt. There's some human drama. Jenny wants to go out looking for her parents. And so Doug leaves with two soldiers to save Jenny's folks. (Shouldn't the soldiers' priority be the hundreds of creatures out there right now, genociding Merry Olde England?)

After they've left, the remaining soldier, a sergeant (Craig David Dowsett), says, "Don't worry, I sent them with two of my best men." Well, your only men, actually.

As in many formulaic, low-budget efforts, the characters are broadly drawn, their emotions and actions shifting according to the needs of the plot (rather than staying consistent to the character or appropriate to the situation). The two female club goers are unnecessarily obnoxious (maybe to show us that they're "strong women"?). Many characters make ridiculous decisions, putting their lives at risk for the silliest of reasons. Especially the soldier who was safely hidden from the monster, which might have passed. Only then the soldier lit a flare and taunted the monster. Why?

The body count is high, though much of the killing is offscreen. A splash of blood, or creative use of shadows. The military base looks like any large building's basement. The CGI monsters look CGI, but they get the job done. It shouldn't be a problem if one suspends disbelief.

The final scene is nicely composed and surprises us with a quickie final battle for Earth's survival. Megan Purvis (It Came from Below) is the film's standout performance, infusing Jenny with some emotional depth.

The Area 51 Incident is like a lot of other films, but it's enjoyable enough if you're in the mood for this subgenre.