You have to hand it to a horror movie that finds thrills and scares in a premise without having a massive budget with which to work.
But they can't all be District 9. Though Monsters wants to be, it runs out of ideas long before it runs out of movie.
The set-up is simple: An American space exploration probe, designed to bring back samples of alien life from distant galaxies, breaks up upon reentry and crashes in the jungles of central Mexico. That was six years ago. Before long, new life forms introduced themselves -- and Earthlings aren't happy about it.
So a whole chunk of Mexico, the one-third just south of the American border, has been designated the "infected zone." The USA has built its version of the Great Wall of China from the Gulf of Mexico to the Pacific Ocean to keep the marauding life forms from invading American soil.
(Gee, what a delicate metaphor for the fear of illegal aliens.)
The film starts with an American photojournalist named Calder (played by an actor with the unfortunate name of Scoot McNairy), who is cruising central Mexico looking for a money-making photo: a child killed by one of the monsters that are terrorizing the countryside south of the border. But he gets a call from home: The owner of his newspaper's daughter is in Mexico, and it's now his assignment to put her on the last ferry back to the USA.
Her name is Samantha (Whitney Able) and she's bright, bilingual and a hottie in cut-offs and a skimpy top. But she's a burden to Calder, who just wants to get his photo and sell it. They head for the port and he buys her the ferry ticket -- for a cool $5,000. But (in the first of the film's plotline stretches) when the engaged Sam turns down Calder's advances, they separate for the evening and, for whatever reason, he hangs on to her passport, ticket and money. He goes out drinking and hooks up -- only to find in the morning that his companion for the evening has run off with all of his valuables (except his camera).
No ticket, no ferry. So they have to take the cross-country route: up-river by boat, then cross-country with guerrillas of some sort. The locals are all relatively good-natured, considering that the Americans have afflicted their country with a marauding race of creatures -- which are the size of cargo cranes and look like ambulatory octopi -- and then closed the door on any escape.
The monsters are a frightening presence that are more often heard than seen. Their attacks are suggested but glimpses of the actual tentacled behemoths are kept to a minimum.
Unfortunately, any concern we might develop for these two central characters also is minimized, in part by an underwritten script by director Gareth Edwards, in part by lackluster performances by Nairy and Able. Able is the more inviting of the two actors but she mostly spends her time reacting to whatever Nairy is mumbling.
District 9 actually developed characters you could care about, even as it told a story of surprising complexity, in terms of both character and plot. But Monsters is a yawn by comparison: a movie that expects you to bring more to the movie than the movie brings to you. That's not much of an entertainment value.