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!