Infinity Ring: #1 Mutiny in Time

When best friends Dak Smyth and Sera Froste stumble upon the secret of time travel-a hand-held device known as the Infinity Ring-they're swept up in a centuries-long secret war for the fate of mankind. Recruited by the Hystorians, a secret society that dates back to Aristotle, the kids learn that history has gone disastrously off course. Now it's up to Dak, Sera, and teenage Hystorian-in-training Riq to travel back in time to fix the Great Breaks...and to save Dak's missing parents while they're at it. First stop: Spain, 1492, where a sailor named Christopher Columbus is about to be thrown overboard in a deadly mutiny!