Mercer's brother, an amateur pilot, crashes on an island and is killed by a giant spider. A year later, when Mercer goes in search of him, she discovers a breed of poisonous arachnids ready to attack.

Efter att en rysk rymdstation krockat med en meteorit sprids delarna ut i rymden varpå en bit landar i New Yorks tunnelbanesystem. Där upptäcks en ny giftig spindelart – de växer sig snabbt gigantiska och hotar människorna i New York. Nu är det upp till förmannen Jason och forskaren Rachel att rädda världen från hoten på åtta ben – innan militären hinner skrida till verket med sina lömska planer.

Deadly spiders are accidentally unleashed from a top-secret military installation. Army specialists and Tanks are called in to exterminate the deadly predators, but the outbreak is worse than expected. Weapons of mass destruction have little or no effect on the venomous spiders. Civilians are strangled with spider webs and eaten alive. The Military in a desperate effort to eradicate the killer spiders, decide to demolish the entire city.

When flying spiders wreak havoc on a small town, it's up to the locals to contain them before the airborne arachnids take over the world.