Before joining Banshee in training the young mutants of Generation X at Xavier's School for Gifted Youngsters, Emma Frost led another group of neophytes, the Hellions, who were slaughtered while under her tutelage. Now, her guilt over the death of her old students is threatening her new ones—as strange ghostly manifestations that resemble the Hellions are wreaking havoc throughout the campus. The teenagers of Generation X must stop these ghosts—if they truly are ghosts—before it's too late.