Martin Bayerle and his estranged son, Grant, return to the wreck that nearly destroyed their family, and begin an expedition which could be their last chance to solve the mystery of the RMS Republic and recover over a billion dollars of treasure.

Martin unravels more of the mystery behind the Republic's treasure. And, during an attempt to recover the gold a panicking diver has an accident that puts his life in jeopardy and threatens to shut the mission down.

When the ship's generator fails, and diver Mark's condition worsens, the crew must head back to port. And a devastated Martin recalls his failed 1987 Republic dive and the crushing effect it had on his life.

Martin follows the money trail through history and identifies a mysterious transaction with a Russian banker that may prove the gold is aboard the RMS Republic, while he and the salvage crew return to the wreck and zero in on her bounty.

When a diver gets tangled in the wreck, and another line compromises the ship's propeller, Tim suits up and dives into harm's way. Martin quarrels over the location of the gold chamber. Plus, the shooting that landed Martin in prison is finally revealed.

A dive on the port side of the wreck yields a piece of the past, and a suspicious boat is spotted nearby.

Grant challenges his father's strategy and forces a new approach to recovering the bounty of the Republic.

The crew makes a run at Republic's treasure, and faces down a destructive storm.