At the outbreak of World War Two, the Bank of England was shipping gold to America to purchase arms and munitions. In June 1940, RMS Niagara was secretly carrying 8 tons of British gold when it hit a German mine and sank off New Zealand. The Royal Navy declared salvage was impossible because the water was too deep, so the desperate Bank of England offered the job to a retired sea captain, John Williams. Within weeks, Williams hired a deep-sea diver, built an experimental diving bell, employed a team of misfits, and refloated a rusting hulk to use as a salvage ship. Then, against orders, Williams sailed into the minefield to search for the sunken liner.

Over the coming months, the crew battled bureaucracy, storms, German mines, and each other, as they dove to record depths. But the closer they got to the gold, the more they realised they would be betrayed by the people who sent them on their mission. With exclusive access to diaries, reports, logbooks, correspondence and interviews, Jeff Maynard tells a story of underdogs overcoming insurmountable odds, and the people of a small coastal community who welcomed them, revealing the truth behind one of the most incredible adventures of the Second World War.