The Alchemist War — John Seven

When their parents, two temporal researchers who travel through time to document history, are transferred to 16th-century Prague, Dawk and Hype hardly expect to find themselves in the middle of an alchemical mystery. In fact, the new, boring job is meant to be a punishment for Dawk and Hype's bad behavior at their last temporal post. The two teenagers are from the 25th century -- how could medieval Prague compare? But when they meet a man who claims he can turn metal into gold, Dawk and Hype find out that Prague holds deeper secrets.