Danny Fenton is losing his mind! At least, that's what Jazz decides when her little brother starts acting strangely and fighting ghosts that aren't there. In reality, Danny is being tormented by a revenge-seeking Youngblood, who cannot be seen by adults -- or by big sisters who think they're adults. When Jazz sells the family on a ghost-tech-free camping trip, Youngblood follows and unleashes a series of juvenile attacks that make Danny seem even crazier, and put the Fenton family in danger.