Princess Kati, an old friend of both Buck and H.H., is about to become Sultana. However, some of her staff are plotting against her and various attempts are made on all three of their lives.
Filmmaker Flynn wants to make movies starring Frank Buck, who reluctantly agrees to have Flynn accompany him on a trip to the Valley of the Mists. The peaceful tribe that lives there is coping with some unwelcome European visitors.
Frank and Gloria's plane goes down in cannibal territory. While they try to get home, they remain unaware that Buck has been infected with cerebral malaria and needs to get treated as soon as possible.
Frank Buck finds an old journal that may lead to finding the bones "Singapore Man", possibly the missing link. Anthropologist Laura Davies arrives as soon as she can, but there are several other parties after the bones as well.
Buck helps a young missionary and her charges escape from Japanese soldiers while trying to reach Gloria to warn her about a spy who has infiltrated an important conference at Raffles.
Down on his luck WIlmer Bass sells his trained lion to Frank Buck. Neither of them realize that the animal's collar is the fabled collar of Katumba that a dangerous cult is searching for.
US Consul in Singapore hires adventurer Frank Buck to take her to a remote jungle area where a plane carrying a US secret agent in possession of stolen Japanese plans for invading Malaya and Singapore has crash-landed.
Gloria counts on Frank Buck to guide an important visitor from Washington going by the name of Marsh. Two sets of German spies are after March, one of which has switched his suitcase for one carrying a bomb.