There are two reasons aliens would invade Earth.

Either they're friendly scientists trying to do research as was the case in E.T. The Extraterrestrial, Close Encounters of the Third Kind and Starman.

Then again, as in the case of Mars Attacks!, Invaders from Mars and Independence Day, they could be hostile and want the planet for their own.

In M. Night Shyamalan's Signs, mankind's worst nightmare is realized.

Shyamalan says Signs is essentially The War of the Worlds as seen through the eyes and fears of one family.

To his credit, the horror and suspense is not diminished because he doesn't take his cameras beyond one small farm.

When things begin to go bump in the night, Pennsylvanian farmer Graham Hess (Mel Gibson) is already in a state of shock.

The night his wife died in a horrific car accident, Graham lost more than his soul mate.

He lost his faith. Graham was a much-beloved pastor but he immediately stepped down from his ministry because he could no longer believe in a benevolent God.

Graham's faith is about to stand an even greater test.

He will be forced to believe in aliens and will then have to call upon the mercy of the God he abandoned to help him save his already-ravaged little family.

CREEPY SCARE TACTICS

Signs works remarkably well because Shyamalan has enough faith in his own story-telling to play the material as straight and serious as possible.

His approach is reminiscent of the creepy scare tactics in Steven Spielberg's Poltergeist, which suggests the horror is not just possible but is happening.

Gibson is able to show Graham's fears and pain without resorting to histrionics.

It is a carefully modulated performance that achieves some genuinely devastating peaks particularly in a dinner scene in which Graham tries to prepare what he fears is his family's last supper.

This is one of Gibson's finest, most mature and heartfelt performances and it won't go unnoticed come Oscar time.

Shyamalan manages to coax as believable and touching performances from Rory Culkin and Abigale Breslin, who play Graham's young children.

A story as tense and suspenseful as Signs needs some honest comic relief, which is provided by Joaquin Phoenix as Graham's younger brother Merrill.

Where Graham is constantly trying to suppress his emotions, Merrill wears his on his sleeve. That Phoenix captures this without losing any sympathy or credibility is a testament to his skill as an actor.

Veteran stage actress Cherry Jones was a perfect choice to play the county sheriff, Caroline Paski.

She has to be the voice of reason. She is the one who must doubt until it's no longer possible to deny what is really happening.

Her scenes with Gibson are achingly real.

In Signs, Shyamalan does for aliens what he did for ghosts in The Sixth Sense.

He makes us believe in their existence, if only for two chilling hours. (More on Signs)

(This film is rated PG)

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