The summer blockbuster Signs is a 1950s B movie wrapped up in 21st-century finery. This goofy smorgasbord of a film juggles questions of faith, terrifying shock cuts and comic asides with admirable dexterity. Most of all, it is a cinematic paean to famous genre films like The Birds, Invasion of the Body Snatchers, Night of the Living Dead and any number of low-budget alien adventures that feature lines like "Resistance is futile, puny Earthlings!"

Although photos of ominous crop circles have been plastered on television and in newspaper ads for the last few months, they play only a tiny role in the film. When the signs first appear in the corn fields of Pennsylvania farmer Graham Hess (Mel Gibson), it looks as if the film is going to be a thoughtful sci-fi mystery in the vein of Close Encounters of the Third Kind. This perception is heightened when we discover that Graham is a former Episcopal priest who handed in his round collar six months earlier. (He has to remind people not to call him "Father" anymore.)

We quickly learn that Graham lost his faith and gave up the priesthood after his wife died in a car accident. He holds God responsible for her death, and we are set up for Graham's rocky relationship with God and for the discussions of faith that come later in the film. As the film begins, Graham is living in the gloomy family farmhouse with his ten-year-old son Morgan, his five-year-old daughter Bo and his younger brother Merrill (Joaquin Phoenix). Merrill, a former minor league baseball player, has moved in to help out in the absence of the kids' mom.

Writer/director M. Night Shyamalan doesn't waste any time getting to the core of the story. First, the crop circles appear in Graham's field and in various locations around the globe, complete with stylized twists and arrows. Are they a signal? A greeting? Or a road map for the aliens to attack?

In true "Wait, wait, we have a bulletin!" movie style, the menace gradually grows worse, until it becomes clear that the aliens--scaly creatures who resemble distant cousins of the Creature from the Black Lagoon--are indeed malicious.

Shyamalan builds the tension and tightens the screws until the Hess family has boarded itself up inside the house. (That should keep the spaceship-flying aliens out, right?) At the same time the director keeps feeding two other streams. One is the low-key comedy provided by the children. The son, for example, buys a used book about aliens, reads it from cover to cover, and becomes convinced that by wearing a tinfoil hat he will prevent the aliens from reading his mind.

Shyamalan's focusing on a child such as Morgan is not new either. His other films (The Sixth Sense and Unbreakable) also include the perspectives of young boys.

The other thread is the recurring notion of faith. Graham continues to wrestle with his damaged belief in God and the question of fate versus coincidence, issues that become more pressing as the possibility of death increases. As the alien apocalypse approaches, Shyamalan adds a wonderful twist. He has Graham hold his children and tell them about the day they were born. In that way, the father circumvents the smoldering questions of immortality and heaven and brings everyone back to memories of the mother.

The end of Signs is too cute, and the final image too pat. But it's hard not to like a film that is so keenly aware of its cinematic roots, and tries valiantly to address issues of faith, forgiveness and redemption even as spaceships hover overhead.