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.

Explorer Academy features: Gripping fact-based fiction plot that inspires curiosity with new technology and innovations; amazing inventions and gadgets; a cast of diverse, relatable characters; secret clues, codes, and ciphers to track down within the text; vibrant illustrations; elements of STEAM; National Geographic explorer profiles in the "Truth Behind" section.

Complete your collection with:

• The Nebula Secret (1)
• The Falcon's Feather (2)
• The Double Helix (3)
• The Star Dunes (4)
• The Tiger's Nest (5)
• The Dragon's Blood (6)
• Explorer Academy Codebreaking Activity Adventure
• Explorer Academy Ultimate Activity Challenge
• Explorer Academy Field Journal
• Explorer Academy Future Tech