Books in A Biff Brewster mystery adventure series

Burma! Biff Brewster can hardly believe he'll soon be flying to Burma to visit his Uncle Charlie. Not even when a green jade ring comes hurtling through his bedroom window is he fully aware of the excitement and danger awaiting him. Is the ring a good-luck charm or a bad omen? Biff suspects that Uncle Charlie's sudden departure from Cape Canaveral to Burma might well have international implications, and that the ring is a warning. But even with a warning, Biff is still a boy alone in a strange country. As he disembarks at Rangoon, the young adventurer walks straight into an attempted kidnapping. Using his wits, Biff escapes from his captors only to learn that his uncle is somewhere in the heart of Red China, perhaps in serious trouble. Horrified at the news, Biff persuades Chuba, a Burmese boy, to lead him through a jungle swamp and across the Chinese border. Once in forbidden enemy territory, Biff uncovers the strange meaning of the jade ring, learns of the secret mission which has brought his uncle to Red China, and discovers a startling project of vital importance to the United States.