Amid assignments that take the Explorer Academy recruits from the iceberg-filled waters of Antarctica to the bone-dry deserts of Argentina, Cruz Coronado is scrambling to complete the last piece of the cipher. With Nebula agents and the elusive explorer spy still out there, his opportunity to recover his mother's world-changing formula is slipping away. But as Cruz has learned from his time aboard Orion, true explorers must never give up. Even after completing dozens of high-risk missions and traveling to all seven continents, Cruz could never prepare himself for one ultimate surprise.