Buffy and the Scooby Gang (the name was Xander's idea, he's workshopping it, it probably won't stick) delve deeper into the heart of Sunnydale's underbelly-and make a shocking discovery about the true nature of the Hellmouth. Meanwhile, Drusilla-AKA THE MISTRESS-sets her sights on Cordelia, as Cordy and Spike find accidental common ground.