Dr. Ira Kane (David Duchovny), a disgraced former government scientist banished to a small community college in Arizona, tags along with his friend and colleague, geology professor Harry Block (Orlando Jones), when he's called to investigate a meteor crash site by young Wayne (Seann William Scott), a hapless fireman wannabe. Dr. Kane is the first to discover the meteor's alien stowaways, and to understand the significance of their rapid development. It's impossible to keep a discovery of this magnitude under wraps, and it isn't long before the government, in the person of beautiful but all-business epidemiologist Allison (Julianne Moore), swoops in to take over. The fate of the Earth hangs in the balance as they try to control an unprecedented and unpredictable alien population explosion.