Sam's fear of rats takes him to the verge of terror. When super-sized vermin turn up in his apartment, his phobia pushes him over the edge. But it isn't one or two rats. A hybrid colony - genetically superior, strong, and super intelligent - has moved into the basement... and living flesh is on the menu. Pets and tenants disappear, leaving behind a wake of carnage Sam is powerless to stop. Now, with his estranged son Bradley dumped on his doorstep, Sam must switch into protection mode - if he can. Faced with impossible odds, Sam hires Bertha O'Connor from Detest-A-Pest Exterminators Inc. She runs the only outfit brave enough - or crazy enough - to take the job. O'Connor and her crew need backup and drag Sam and Bradley along for the battle. But this horde of super-rats may be smarter than anyone had bargained for...