Special Installation MX-3 in Washington, D. C. is protecting a renowned cryptographer and head clerk of a U.S. intelligence installation, Dr. Waldo E. Bannister, responsible for breaking the Manchurian Code. With his knowledge, expertise, and photographic memory, he is highly sought after. Deep in his brain are the files of twenty-one of the country's best agents, including Burke. In retirement, Bannister travels to the Isle of Tio Moro, a thieves market where the most unusual items regularly change hands and the home of the notorious Mr. Sin. Planning on selling his information, Bannister is instead captured by Mr. Sin, who plans to auction off Bannister's facts to the highest bidder, keeping the money for himself. Burke is sent to either retrieve Bannister off the island or kill him before he talks. Posing as a playboy who operates on the fringes of the law, Burke gains the confidence of Mr. Sin and plans to bid on Bannister.