When a cockroach-spread plague threatens to decimate the child population of New York City, evolutionary biologist Susan Tyler and her research associates rig up a species of "Judas" bugs and introduce them into the environment, where they will "mimic" the diseased roaches and infiltrate their grubby habitats. So far, so good, until the bugs keep on evolving and learn to mimic their next prey – humans.

Mimic intrigues for a while, but it doesn't quite stay the distance.

The remedy is sometimes more painful than the problem: in Mimic that's what scientist Susan Tyler (Mira Sorvino) discovers to her cost. She succeeds in vanquishing a plague of disease-carrying cockroaches from the streets of New York by breeding a colony of roach-eating insects; the trouble is that, three years later, the bugs she bred are getting bigger, and they're hungry for blood – human blood.

Mexican director Guillermo Del Toro and his co-screenwriters, who include John Sayles, have set up an interesting premise with Mimic, which is clearly intended to be a thinking person's horror film, much like the Alien series. For most of its length it succeeds; the monsters are pretty terrifying creations, and there's a ruthlessness to the film which is refreshing. But, in the end, it's just a monster picture.

Del Toro, whose Mexican film Cronos became a cult item, fails to bring much needed originality to the picture. Part of the trouble is a lack of really interesting characters with which the audience can identify, though Mira Sorvino proves to be a resourceful heroine – and there are plot inconsistencies, too. Mimic intrigues for a while, but it doesn't quite stay the distance.