Bruce Brewster, or Biff, is a blond-haired sixteen-year-old with keen, expressive blue-grey eyes and a strong-featured face. He's big and husky for his age, with broad, square shoulders, and is already taller than his mother. He lives in Indianapolis, Indiana with his parents and two siblings. His family also owns a cottage on a lake near the coast of southern California where he skin dives and enjoys other sports. Biff is a dash man on his school track team and enjoys fly fishing and hunting quail with his father in Indiana. Biff's ham radio call sign is W 5604 J, he already has his driver's license, speaks Spanish, a little Portuguese that he learned from his father, and reads French well enough to understand. He also learned to play a good game of chess from his Uncle Charlie. Biff hopes to attend Notre Dame when he finishes high school, but he enjoys travelling with his father when he's able in the meantime.

Thomas R. Brewster is a tall, rugged man with dark hair and a tanned, square-jaw face. He is practically an older counterpart of his son Biff except for the hair. He fought in the South Pacific during WWII as a Junior Navy Lieutenant, and worked his way up to Lieutenant Commander before leaving the service. He is an excellent marksman specially trained for jungle fighting, and has won medals for bravery. He also has had bomb demolition experience, but now works as the chief field engineer for the Ajax Mining Company. He has made many contributions to the field of mining, and is well respected. He is also an amateur mountain climber and member of Alpinists clubs on three continents.

Martha Brewster is a wife, and the mother of her three children, Biff, Ted, and Monica. She has a pleasant, friendly face with arched eyebrows.

Ted & Monica Brewster are Biff's eleven-year-old twin siblings. They are eager to share in Biff's adventures abroad, and are always disappointed whenever they are left behind. They still look forward to the tales he brings back from his travels with their dad to the four corners of the globe, however. Monica is the older of the two (by ten minutes), and has hazel-colored eyes, copper hair, a straight, sturdy figure, and a great fondness for the telephone. She and Ted are quick to disagree with each other, but they can never stay angry for long.

Charles Keene is the brother of Martha Brewster, and therefore Biff's uncle. He attended Butler University in Indianapolis and was in the Navy for several years. He flew fighter planes during the Korean conflict and traveled as much as he could about the Orient on his furlough time. Charlie remained in the Navy following Korea, and became a pilot in the squadron of planes assigned to tracking and retrieving test missiles fired from Cape Canaveral into the South Atlantic. After two years there, he decided to return to the Orient that fascinated him so much. He resigned his commission and joined an old pilot friend in establishing a fleet of planes for Explorations Unlimited in Burma. He's also a good cook, can handle a boat, and skin dive as well.

Warren Becker is Biff's uncle, a well-built man of about thirty-five years and medium height. He is a well-known amateur hunter in Kenya, and has travelled quite a lot elsewhere.

Muscles is a burly airplane mechanic from Kentucky with unruly red hair and a wide, freckled face. He is as big as a football linebacker, and his enormous strength leaves no doubt where his nickname comes from. He has known Charlie Keene since they were together in the Korean War, and has worked with him at Explorations Unlimited in Burma. Besides airplanes, Muscles also has experience with blimps and stratosphere balloons.

Shake Lakum is a very tall, very thin bush pilot with pale blue eyes who owns Lakum Airlines based in Cordova, Alaska. He is an excellent pilot used to flying in rough weather and taking off from or landing on rugged Alaskan terrain. His real name is Thomas, but the nickname "Shake" comes from his Indian passengers who say he "take'um and shake'um, but no break'um." A mechanic named Charlie maintains the company's small hangar and aircraft, including a small Piper called Tumblebug, a DC-3, and a bright yellow Cessna ski-plane with red trimming called the Williwaw, an Eskimo word meaning "whirlywind."

Kamuka is a lithe Brazilian Indian with dark hair and eyes. He is about Biff's size and age and speaks excellent English and Portuguese in addition to his native tongue. Growing up in the jungle has given him a great deal of practical jungle lore, as well as many useful skills. He has worked as a native bearer for expeditions travelling through the interior, and now attends technical school in Brasilia, the capital of Brazil.

Chuba Chin Fu is a thin faced Chinese boy of almost sixteen years of age, and stands half a head shorter than Biff. He has long, black, wiry hair that is usually plastered down with smelly hair tonics, and his skin is so deeply tanned that its yellowish tinge from his Chinese blood hardly shows. He looks more Burmese than Chinese, but his one passion is to be "like American kid." In this vein, he reads any American magazines and comics he can get ahold of, and tries to speak American jive with mixed results. His father, Ti Pao, is in charge of the native workers at Explorations Unlimited in Burma. Chuba is resourceful, has a quick Oriental mind, and is equally at home in the Chinese jungles and mountains from his frequent travel across the border from Burma.

Likake Mahenili is the fifteen-year-old son of Ajax Mining's Hawaiian representative, Hanale Mahenili. He has a round, bronze face with an eager expression and deep brown eyes. His build is slightly smaller than Biff's, but he is very wiry and athletic. He lives on the island of Oahu in a beach-front home on Waimanalo Bay with his parents and eleven year old sister, Wikolia. There he attends Kamehameha School, a private school for boys and girls of Hawaiian ancestry. Li, as his friends call him, is an expert swimmer, having been in and around water all his life. He's good with a surfboard or any kind of boat, and can skindive up to fifty feet as well as hold his breath for more than three minutes.

Miguel Arista is the nephew of Judge Felix Arista, a famous Mexican official and the head of an historical society in Mexico City. Mike, as he is called in English, is a well spoken dark haired Mexican boy of about sixteen years.

Monda is a native of Tanganyika about the same age and size as Biff. He speaks Swahili and English, and is an excellent runner. He attended the Missionary School in Dar es Salaan and has worked as a native helper for a safari guide in Kenya. He now attends the Royal Technical College in Nairobi.

Tish is a roly-poly Alaskan boy about Biff's age with brown skin, brown eyes, and dark hair. His Eskimo mother died in a fire at their cabin when he was a baby, but was able to get Tish outside. Shake Lakum had landed to try to help after spotting the fire from the air, but found the baby alone. His father (presumed to be a Tlingit Indian) was never found, so Shake raised the boy himself, and named him after Tish's pronunciation of "Thomas." Tish serves as copilot when flying with Shake, and is a competent pilot on his own. Like most Eskimos, he can't swim, but he is a surprisingly fast runner despite his bulk, and has good tracking skills. Besides English, Tish also speaks Tlingit and Chinook, the latter being a kind of Alaskan language made up of Eskimo, French, Spanish, English, pig Latin, and a little Hawaiian.

Chandra is a Hindu boy from Calcutta whose slenderness makes him look tall, though he is in fact half a head shorter than Biff. He has a self-possessed air about him, a surprising strength in his wiry form, and his dark eyes have a wise gleam in them. Chandra works for a Bengal street magician named Jinnah Jad, and speaks excellent English in addition to Hindi. His many skills include snake charming and the art of well jumping which he learned from his great-great-great-grandfather near Delhi. He also has an uncle who is the town clerk for the village of Supari in India.

Derek Zook is a boy Biff's age from the Netherlands. He speaks English with almost no trace of accent, and astonishingly looks enough like Biff to be his twin. Derek has the same well-muscled athletic body, short cropped hair, and the same height. The only slight differences are his barely darker hair, and eyes that are a deeper shade of blue. His mother died when he was a boy, and he now divides his time between Curaçao where is father is a pearl fisherman, and Holland where he lives with his grandparents while attending school. Like Biff, he has also had his share of travel and adventure, including skin diving in the Mediterranean and cross-country skiing in Switzerland.

Tazling Norkay is a Sherpa boy about Biff's age who was born in Katmandu. His head is rather flat-topped, he has a small nose, and he has the the same black, silky hair, dark brown semi-Oriental eyes and short wiry body as his father, a famous Sherpa guide named Izling Norkay. Taz is at home in the mountains of Central Asia, and has a remarkable ability to identify shapes and forms at great distances.

Peter Balsam is the towheaded son of Sir Charles Balsam, the director of the Royal Atomic Research Laboratory at Edensboro, England. Peter attends Harley School for boys just outside of London, and has a great fondness for detective novels.

Ahmed Kadir is a gaunt Arab boy about Biff's age, with dark brown eyes. He is the mirror image of his father Khalil, an engineer for the Aramco Oil Company in Saudi Arabia, in whose footsteps he plans to follow. Ahmed has won a scholarship to study in the United States, but currently attends Aramco City high school. He speaks excellent English in addition to Arabic, and is also the proud owner of a beautiful golden stallion named Suji, and a female camel named Zenobia. Both were gifts from the royal stables in appreciation for the rare type blood transfusions Ahmed donated during an illness of the prince. Ahmed is very familiar with traditional desert travel, and has learned many skills such as tracking and navigating by the stars from his Bedu grandfather.

Junius Croz is a brown-haired boy about Biff's age who lives with his family in a fair-sized farmhouse a few miles outside the town of Hautburg, Switzerland. His father is a Swiss Army officer, and Junius also has two younger siblings: a sister named Clauding and a brother two years younger named August. Their grandfather Lycurgus Croz is the best watchmaker in Hautburg, and works from a small workshop in the house where he is teaching Junius the trade. Junius speaks several languages including Romansch, Italian, French, German, and English, and enjoys skiing whenever he can. He also owns a highly trained medium-sized shepherd dog named Otho. Otho looks something like a collie, but always tries to act like a St. Bernard. He has an unerring sense for finding avalanche victims buried under the snow and he and Junius are always ready to help when they are needed for such an emergency.

During his travels Biff has visited many countries all over the world. While some countries have merely served as refueling stops en route to his main destination, he has at least landed at all these nations: Brazil, Burma, China, Egypt, Great Britain, Haiti, Hong Kong, India, Italy, Japan, Kenya, Malta, Martinique, Mexico, Morocco, Nepal, Netherlands Antilles, Saudi Arabia, Spain, Sudan, Switzerland, Tibet, Uganda, and Venezuela. Alaska and Hawaii also deserve mention since they had only recently become states, and were practically foreign countries themselves.