Kingdom Keepers: The Return Series by Ridley Pearson

With the defeat of the Overtakers behind them, the five teenagers known as the Kingdom Keepers should be celebrating. By all accounts they saved Disneyland from certain destruction. Why then did their mentor leave one last puzzle for them to decipher? The Keepers must solve a puzzle of the past, or be crushed under an evil that makes the Overtakers seem like gentle souls.

Disneyland, Opening Day, 1955. When five present-day teenagers known as the Kingdom Keepers find themselves thrown into a past that would make anyone envious, things don't exactly work out the way they'd hoped. Finn, Charlene, Maybeck, Willa, and Philby open a door into a place and a time when the legend of the Disney parks is just starting. They are there, in 1955, to retrieve Walt Disney's infamous pen that once saved the parks as we know them... moreDisneyland, Opening Day, 1955. When five present-day teenagers known as the Kingdom Keepers find themselves thrown into a past that would make anyone envious, things don't exactly work out the way they'd hoped. Finn, Charlene, Maybeck, Willa, and Philby open a door into a place and a time when the legend of the Disney parks is just starting. They are there, in 1955, to retrieve Walt Disney's infamous pen that once saved the parks as we know them. But like all things Disney, nothing is as it seems.The early days of the Tower of Terror, the origin of the Overtakers (Disney villains), and the real power of magic unfold in an unexpected series of events that propel both the Keepers and Disney itself into a darkness no one saw coming. Along the way, the Keepers visit Walt Disney's hilltop home, Disneyland's opening day and reception, and find themselves separated from friends sixty years away. The three Fairlies, young women in Disney's School of Imagineering, girls with astonishing powers of their own, have unmasked a long-buried secret that threatens the lives of their friends as well as everything Walt Disney worked for. less

The stakes are high--both for the past and the future. The finale of The Return series leaves the Kingdom Keepers with unimaginable choices to make.