Dir: M Night Shyamalan. US. 2002. 106 mins.

In the hands of a less gifted director, Signs could have turned out an embarrassing mess. As it is, however, commercial auteur M Night Shyamalan just about manages to pull off what appears, on the face of it, to be a very curious blend of family drama, spiritual quest and alien invasion thriller. With a UFO theme and Mel Gibson as marketing hooks, the film should attract a broad and sizeable audience, though the final US gross will probably be closer to the $95m achieved by Shyamalan's Unbreakable than the $294m corralled by his breakout debut, The Sixth Sense. Gibson's presence should also help extend Shyamalan's strong track record in the international marketplace, where both The Sixth Sense and Unbreakable earned more than they did in the US (57% and 62% of their worldwide grosses respectively).

While crop circles provide the central motif in Buena Vista's aggressive marketing campaign for the film - 250 of the mysterious formations appear around the world every year, according to the distributor's press materials - the phenomenon itself is passed over fairly quickly in Shyamalan's script. Gibson's Graham Hess is a former Episcopalian minister who, after the tragic death of his wife, has lost his faith and turned instead to farming. When he discovers a pattern of circles and lines carved into his crops, Graham's first instinct is to protect his two young children (Culkin, from You Can Count On Me, and Breslin) from the local thugs who he thinks must be responsible. But the sinister signs begin to multiply and, when the circles turn out to be part of a global navigation system for a force of alien invaders, Graham, his brother Merrill (Phoenix) and his kids are forced to barricade themselves inside their rambling farmhouse as they wait for the evil aliens to appear.

The story's juxtaposition of domestic conflict with a supernatural - and, in this case, extraterrestrial - theme echoes the concerns of Shyamalan's first two films. But whereas those films blended their elements into a consistent whole, Signs goes through regular - sometimes none too smooth - changes of tone and focus. Over its first third, even as the alien invasion gets underway, the film plays surprisingly often for laughs, coming across almost as a family version of a lighthearted X Files episode (crop circles, Merrill assures his nervous nephew and niece are just the work of "nerds without girlfriends.").

The surprise later on is that Signs contains none of the usual scenes of laser beam-spewing space ships and confines its action to the Hess household, where the global crisis, glimpsed only through TV news coverage, begins to prompt Graham to reconsider his loss of faith. There are a few crowd-pleasing jolts and when an alien does finally appear he is a suitably nasty piece of work. But hard-core sci-fi fans drawn by the film's marketing campaign will be disappointed by the dearth of ET action. Even casual audiences may wonder why aliens who have managed an inter-planetary invasion have so much trouble getting into the cellar of an ageing farmhouse.

Shyamalan takes some big risks with the shifts in mood, and the mix of laughs and terror is something that only the director's hero, Alfred Hitchcock, has ever really mastered. Certainly Signs never achieves anything like the assured tone or confident style of The Sixth Sense. What it offers in their place is a quirky charm and some touching interactions between the fragile Graham and his friends and family.

As he did in both his previous films, the writer-director gets some engaging performances from his cast, though there are also times when the acting seems over directed. Gibson is a good choice to take over the role of the spiritually troubled everyman from Shyamalan's The Sixth Sense and Unbreakable star Bruce Willis. In the absence of a romantic co-lead - the nearest thing to it is the local policewoman (Jones) who senses Graham's emotional turmoil - Phoenix does a capable job as Graham's admiring younger sibling. Shyamalan's knack for picking child performers continues with Culkin and Breslin, who bring, respectively, emotional depth and considerable charm to their roles. Behind the camera, The Sixth Sense cinematographer Tak Fujimoto creates some atmospheric lighting effects and production designer Larry Fulton (a Shyamalan regular) gives the Hess farmhouse a satisfyingly lived-in feel.

Prod co: Touchstone Pictures, Blinding Edge Pictures, Kennedy/Marshall Productions
US dist: Buena Vista
Int'l dist: Buena Vista International
Prods: Shyamalan, Frank Marshall, Sam Mercer
Exec prod: Kathleen Kennedy
Scr: Shyamalan
Cinematography: Tak Fujimoto
Prod des: Larry Fulton
Ed: Barbara Tulliver
Music: James Newton Howard
Main cast: Mel Gibson, Joaquin Phoenix, Rory Culkin, Abigail Breslin, Cherry Jones