Game park warden Robert Payton is increasingly angry that his job in Kenya involves the butchery of animals, including acting as guide for big game hunters. He quits his job, gathers support for his National Park project with some difficulty, and sets out with ten African askari, his son Tim and his wife Mary. Mary is very reluctant to leave Nairobi but is given little choice.

On their journey into the bush their truck is charged by a herd of rhinoceros. Tim's habit of adopting animals as pets proves dangerous, especially when he picks up a lion cub, angering its mother. Payton is threatened by a leopard and his life saved by the intervention of an African, who kills it with a spear.

The conservation project is continually under threat. Initially the main threat is from ivory poachers. Payton and the askari see an African killing elephants with poison darts and a fight ensues, but the poacher gets away. Payton names this African 'Scarface'. He visits the chief of his village but the chief denies any knowledge of ivory poaching.

There follows a more general slaughter of animals in the park. Payton, without authority, raids the African village to disarm the villagers and encounters Mainwaring - a man whose journeys into the bush are ostensibly to photograph wildlife and who has visited Payton and his family. The district commissioner has already voiced the view that a European is behind the ivory poaching, and Payton now identifies this European. Mainwaring uses every means at his disposal to scupper Payton's mission, reporting Payton's various breaches of regulations to the authorities as well as slaughtering animals.

Vultures gathering suggest that Payton's mission is failing, but Payton suspects that their next gathering is because the Masai tribe have got into the park with their cattle, bringing disease. Mainwaring reports the arrival of the Masai and threat of disease to the authorities and a vet arrives at the park. Mainwaring subsequently tells Payton that he bribed the Masai to come in.

Payton finds the hidden ivory - the first proper evidence of Mainwaring's activities - and sends askari to fetch the district commissioner. But as Mainwaring arrives to collect the ivory and Payton challenges him, an African throws a poisoned dart at Payton. He lies wounded on the ground as Mainwaring dismisses Africa as 'finished' - no longer a white man's country. Payton declares his own belief in a 'new Africa' in which he has 'black brothers'. After Mainwaring's departure with his ivory, a leopard threatens Payton, but Scarface saves his life.

When the district commissioner arrives, the party pursue Mainwaring, who ultimately crashes over a precipice to his death. The threat from the ivory poachers has been overcome, but there is still the threat of disease. Payton and his family anxiously await the vet's verdict, and are relieved when he tells them there is no disease. The National Park project had seemed certain to fail, but is now well-established as a place where no vultures fly.