Captain Caleb Frobisher arrives in West Africa on a secret mission: following in the footsteps of his brothers, he tries to uncover the mystery of the missing people. He is determined to wrap up the threads, but if he wants to succeed in the mission, he is forced to stay in the jungle for a long time. He meets Kate Fortescue, the pretty governess who was captured by kidnappers and is now the patron of the children working in the mine.