Book One: Young Nate is on a foreign exchange assignment to stay with a family in an ancient castle in western Germany. As he eagerly learns to adapt to the culture, Nate is befriended by neighboring Germans, Thorston and Sandra, who together discover there is something terribly wrong in the castle and the surrounding farming village of Gauersheim.

Book Two: Nate Brighton returns home to America and soon departs with his Christian education/missionary family for the island of Okinawa, Japan. Once settled into this foreign but astonishingly eventful place, Nate and his younger brother and friends set off for a camping trip at the ruins of Nakagusuku Castle.

Book Three: It is one thing to talk about protecting the environment, but it's an entirely different thing to stand up and do something about it. The Connor boys, as you will see, are up for such a task. Nate and Ricky's parents send them home to Washington State from Okinawa, Japan, to stay in their home under the guardianship of their Uncle Hank and prepare for a new school year.