A friend of Carson Drew's has been arrested and charged with sending a truck loaded with explosive oranges into the Space Center complex at Cape Kennedy. Knowing that Mr. Billington could not possibly be guilt of sabotage, Nancy and her father rush to the defense of the accused man. During the Drews' investigation Nancy become suspicious of an old spooky mansion that houses fierce African wild animals on its extensive grounds. Soon, she discovers that something besides the training of wild animals is going on at the mysterious estate. Many dangerous moments await Nancy before she proves Mr. Billington's innocence and thwarts the plans of treacherous subversives bent on undermining the U.S. space program.