
Vlad's up to something and it involves Danny. After he sends three ghosts to Amity Park to battle Danny Phantom, it is revealed that he's working on his creepiest project yet: a clone of Danny Phantom. So far, the clones he creates can't sustain their forms for very long, but Vlad is determined to succeed. Danny doesn't have long to worry about Vlad's ghostly visitors, however, because he's distracted by the appearance of Danielle, a cousin he didn't know he had. And then, Danielle reveals that she too has ghost powers -- she's Dani Phantom! Unfortunately, she's also a product of Vlad's experiments, and therefore an imperfect ghost with an unstable form. Danny must convince his new "relative" to turn on her creator and help him destroy Vlad's evil experiment, before it's too late for both ghost kids.
Danny and Sam get into a fight, and when Sam utters the words, "I sometimes wish I'd never met you," she finds herself in a world in which she and Danny are strangers. Worse than that, since it was Sam who encouraged Danny to check out the Fenton Portal the night he got his ghost powers, Danny doesn't have any powers! Now, Sam must convince Danny that they share a friendship and a history, and lead him back to the Fenton Portal for a second "accident" so he can again become Danny Phantom.
After being bitten by tiny green ghost beetles, the kids of Casper High get a mysterious illness that gives them ghost powers and are quarantined at a spooky old hospital outside of town. When Danny sneaks into the hospital to investigate, he is captured by Penelope Spectra and her assistant, Bertrand. They are the ones who started this illness as part of their plan to build Penelope a young and beautiful new body. All she needs is Danny's half-human/half-ghost DNA to complete her ghostly plan. With Danny captured and Sam sick, it's up to Tucker to conquer his fear of hospitals and free Danny before Penelope gets what she's after.