A research team arrives in Castle Key to explore the wreck of an old smugglers' ship that sank in Pirate Cove. When Scott and Emily dive down to the wreck, Scott glimpses a long lost artefact said to hold the key to a hoard of smuggled treasure. But when the team leader goes back to recover the artefact, it has mysteriously vanished! Was Scott mistaken or is somebody else after the smugglers' loot? Follow Scott, Jack, Emily and Drift on a very mysterious treasure hunt.