A fast-moving middle-grade novel set in the seventeenth century about two Portuguese orphans who are sent to Brazil where they encounter slaves from Africa. Together with their new friend, an aboriginal boy, they work towards reuniting the slaves with their families and helping them escape to freedom

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?