As simple (in a nice way) as its title, opening for Halloween and sure to disappoint most everyone misled by that title, Monsters is obvious from the get-go, boasts a low-key cast of essentially two plus a very few sad special-effects aliens, follows a hoary storyline -- and yet overcomes the drawbacks to emerge rather winning, if small.

British director-writer Gareth Edwards doubled as cinematographer and visual effects expert, logically so with a five-man crew and miniscule $15,000, which even then surely cannot have included travel expenses to and through Mesoamerica. Ad hoc extras were recruited and locations chosen along the way, sometimes geographically incorrectly, as for instance the Mayan step-pyramid moved a thousand miles north to the U.S. border.

Spiritually, the film harks back to sci-fi flickers of half-a-century ago and more. The center story -- for this is a romance that happens to be set against the trappings of extraterrestrial “invasion” -- falls in the long line of Westerns, war, detective and general adventure fare in which the hero is tasked with squiring the heroine through dangers to final safety, family and love (often with him).

Maybe because Monument Valley seems passé in a digital age or else is environmentally protected, and villainous American Indians politically incorrect, Australia’s Outback sometimes stepped into the breach with, say, Crocodile Dundee and Japanese Story, both of whose heroines are also lithe crop-haired blondes and the former also presenting an undesired rich fiancé waiting back in “civilization.”

Short-shorted solo tourist Samantha “Sam” Wynden (Whitney Able) is lightly wounded and stuck far south of the border following yet another of the ongoing battles between the army -- and an air force that appears to consist of two jets and a copter -- and alien life brought back on a crashed NASA probe. From the look of it, the hundred-fifty-foot intruders are having the best of it, leaving buildings in ruins, trains knocked from trestles and flying machines in pieces on the ground in the northern quadrant now a quarantined Infected Zone.

The situation promises manna from heaven for stringer photographer Andrew Kaulder (John “Scoot” McNairy), who gets paid lots for shots of disasters and dead rather than of smiling faces, but his Stateside New World boss orders him to drop everything to escort daughter Sam to the coast, and thence home. His camera not even acceptable as a loan pledge, the boyish McNairy is not impressive when being the billed “jaded US journalist.” The chaste film’s “R” rating comes from his few four-letter words, though thank goodness the heroine is nowhere made verbally with-it. He does get inoffensively drunk and tries to wheedle his way into his charge’s room for a nightcap, air-conditioning and sex. (A biological son he cannot acknowledge but tearfully telephones on his sixth birthday, is a needless outside distraction.) Diplomatically turned down, he drinks more and finds a willing female, who, for plot complication, steals his wallet and both Americans’ passports.

SPOILER ALERT

Land transport canceled and the last ferry having sailed, Sam exchanges her diamonds -- she emphasizes the plural -- engagement ring for illegal overland and boat rides for the two of them. As they pass from guides to armed protectors, they see ruins and wreckage, abandoned military hardware, corpses here and there, fungi-like alien eggs, tentacles and a brief entire clicking adult looking like a cuttlefish with an internal pinball machine.

Man and woman are reduced to two, their characters not delved into, though he does apologize for his tequila-and-beer boorishness. But they turn out likeable while moving towards the inevitable. Despite misfired attempts at depth -- she moralizing about his ghoulish profession; monolithic U.S. border walls inspiring a sentence on seeing home from outside; flattened family dwellings and a crazed shopping-cart lady -- things remain satisfactorily superficial in this type of tried-and-true tale. Aliens sweetly coupling above a service station provide prelude to that first, long-expected kiss and a voiced desire not to return home so quickly after all.

Edwards’ effort is not in scale “an epic science fiction adventure.” Old-fashioned in story and furnishings, pretending to no resolution of its world’s infestation dilemma, it is quiet and appealing for those who ask nothing more than to sit back and relax for ninety-three minutes.

(Released by Magnet Releasing and rated “R” for language.)