Jeff and his team's search for the wrecks of Mary, Joseph, and Neptune takes them further into uncharted territory. When an unusual artifact suggests a nefarious past for one of the ships, Jeff begins to suspect he may be on the verge of uncovering a field of stolen treasure.

A powerful hurricane forces Jeff's team into a secluded cove, where they investigate The Lombrac, a legendary 18th-century ghost ship. As the divers recover intriguing clues from the murky depths, Jeff zeroes in on the site of a 300-year-old mystery that may finally be solved.