Sam Hopwood and Carrots back from the Crimea are on board a ship bound for South Africa and the Cape of Good Hope when they are shipwrecked off the coast of Angola. Sam is now a junior member of the Army Medical Corps and he helps to save many lives. With the help of a boy called Paulo from a local missionary school, the survivors get to the capital city of Luanda safely. It is here that Sam meets the great missionary David Livingstone and accompanies him, along with Paulo, on a great journey to the interior. As they proceed through the jungle on their adventure the boys encounter fresh dangers and Sam has the chance to hone his medical skills. This is a sequel to Sam and the Gold Fever.