Sonia, Pedro and their classmates are baffled.
Mysterious messages keep popping up on their computers, on their mobile phones, on websites they visit, even on a radio programme they listen to. It is a voice from the past - but who is trying to contact them from out of history, and why?
Follow the clues from their school in modern-day Brazil through the ages to ancient Egypt, to a medieval wizard's castle laboratory and to the ships that sailed from Europe to discover the New World. Can you solve the History Mystery?