They Came. They Shopped. They Saved The World!

When a comet hits Earth, nearly everyone is outside to witness the spectacle and celebrate its arrival. Unfortunately, the comet possesses deadly rays that turn all the onlookers to dust. However, teenager Regina and her Valley Girl sister Samantha survive, having been indoors when the comet struck. But the world has become a dangerous place, populated by monstrous zombies, created by the comet's rays. The girls try to escape the creatures and find safety. They seek refuge at a radio station, having been lured there by a (taped) radio transmission. There they meet Hector, another survivor. Meanwhile, scientists from an underground compound find they've been affected by the comet, and need the blood of healthy humans to create a vaccine. They kidnap Samantha to use her for their cure, forcing Regina and Hector to set out and save her - for the sisters are Earth's only hope for re-populating the planet...