This film in the Bomba series finds Johnny Sheffield both finding out his true identity and dealing with a usurper who has taken the leadership of the Masai tribe. The title is a real misnomer, what Sheffield has not done is find a sister.
It seems as though Bomba's real parents were government agents who knew the truth of the coup in the Masai tribe. Martin Wilkins is the usurper and he reals with help of Suzette Harbin who has the meatiest role in the film that of his daughter and chief enforcer. She's a real piece of work and goes out in quite the diva fashion.
Helping Bomba is Walter Sande who is in the Masai village on a survey and his daughter Karen Sharpe and of course that symbol of jungle authority Commissioner Barnes as played by Leonard Mudie, the other recurring character in the Bomba series.
Masai politics and Bomba's identity, makes for a nice film.