This book was written for the Stratemeyer Syndicate by James Duncan Lawrence (who also wrote the majority of the Tom Swift Jr. series) in 1957.[1] Between 1959 and 1973 the first 38 volumes of this series were systematically revised as part of a project directed by Harriet Adams, Edward Stratemeyer's daughter.[2] The original version of this book was shortened in 1966 by Priscilla Baker-Carr[1] resulting in two slightly different stories sharing the same title.
Plot summary
Frank, Joe, Chet and Tony travel to Puerto Rico to investigate the mystery behind a coded letter they received from the Hardy father. They later go in a race against time to stop a criminal mastermind from using an atomic bomb to take over the government of the fictional country of Tropicale.