On hearing about a brewing storm, the sisters are not suprised to discover that a series of freak weather patterns is a harbinger of danger. Piper, Paige and Phoebe learn that the key to preventing this mass destruction may lie in the hands of a young, troubled firestarter who's on the run. If they want to avert the natural disaster, the Charmed Ones are going to have to go straight to the supernatural source.