Inspired by the story of his two cousins that died at sea in WWII, Ross Kemp explores captured German scout warship, the F2 and brings up treasure that could link back to his relatives.

On the coast of north Devon, Ross is joined by Emily Turton, as he prepares to dive down on the wreck of sunken steam ship Iona II. The ship was heading to America in the early 1860s, when it went down with a mystery cargo on board that the owners went to extensive efforts to recover in secret. Ross hopes his night dive might reveal what they wanted back so badly but the wreck is shrouded in dense low visibility which hampers their investigations.

Ross and Mallory dive down to the wreck site of 36-gun Nelsonian frigate HMS Amethyst, a legendary battle cruiser, launched in 1799, which proved one of the most successful and prolific of the Napoleonic wars. Ross makes an incredible find using an underwater metal detector, and the historic item reveals why the ship was such a potent weapon of war but also gives clues as to how and why it sank. It leads Ross, Mallory, and Neil to the 16th century Minera Tavern for a story of trickery and kidnapping by the Royal Navy.