In 1942, when Singapore was being evacuated prior to the Japanese invasion, 20,000 sovereigns were loaded on the schooner Vagabond, but after putting to sea, the boat was never seen again. However, a dead native has now been found in his canoe in the Mergui Archipelago, wearing a necklace made up of the same sovereigns. Biggles, with Ginger and Bertie, befriend McDonald, the captain of the ship that found the dead native and with the help of Chintoo, a local man, they begin the search for the Vagabond. But there's corrupt officials, storms, Chinese pirates and a mad Japanese airman in their way...